Geometry: A Complete Course

Transcription

1 Geometry: omplete ourse with Trigonometry) Module E Solutions Manual Written by: Larry E. ollins

2 Geometry: omplete ourse with Trigonometry) Module E Solutions Manual opyright 2014 by VideotextInteractive Send all inquiries to: VideotextInteractive P.O. ox Indianapolis, IN ll rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the publisher. Printed in the United States of merica. ISN RPInc

3 Table of ontents Unit V - Other Polygons Part - Properties of Polygons LESSON 1 - asic Terms LESSON 2 - Parallelograms LESSON 3 - Special Parallelograms Rectangle, Rhombus, Square) LESSON 4 - Trapezoids LESSON 5 - Kites LESSON 6 - Midsegments LESSON 7 - General Polygons Part - reas of Polygons LESSON 1 - Postulate 14 - rea LESSON 2 - Triangles LESSON 3 - Parallelograms LESSON 4 - Trapezoids LESSON 5 - Regular Polygons Part - pplications LESSON 1 - Using rea in Proofs LESSON 2 - Schedules Unit VI - ircles Part - Fundamental Terms LESSON 1 - Lines and Segments LESSON 2 - rcs and ngles LESSON 3 - ircle Relationships Part - ngle and rc Relationships LESSON 1 - Theorem 65 - If, in the same circle, or in congruent circles, two central angles are congruent, then their intercepted minor arcs are congruent. Theorem 66 - If, in the same circle, or in congruent circles,two minor arcs are congruent, then the central angles which intercept those minor arcs are congruent. LESSON 2 - Theorem 67 - If you have an inscribed angle of a circle, then the measure of that angle, is one-half the measure of its intercepted arc. LESSON 3 - Theorem 68 - If, in a circle, you have an angle formed by a secant ray, and a tangent ray, both drawn from a point on the circle,then the measure of that angle, is one-half the measure of the intercepted arc. Module E - Table of ontents

4 LESSON 4 - Theorem 69 - If, for a circle, two secant lines intersect inside the circle, then the measure of an angle formed by the two secant lines,or its vertical angle), is equal to one-half the sum of the measures of the arcs intercepted by the angle, and its vertical angle. Theorem 70 - If, for a circle, two secant lines intersect outside the circle, then the measure of an angle formed by the two secant lines, or its vertical angle), is equal to one-half the difference of the measures of the arcs intercepted by the angle. LESSON 5 - Theorem 71 - If, for a circle, a secant line and a tangent line intersect...77 outside a circle, then the measure of the angle formed, is equal to one-half the difference of the measures of the arcs intercepted by the angle. Theorem 72 - If, for a circle, two tangent lines intersect outside the circle, then the measure of the angle formed, is equal to one-half the difference of the measures of the arcs intercepted by the angle. Part - Line and Segment Relationships LESSON 1 - Theorem 73 - If a diameter of a circle is perpendicular to a chord of that circle, then that diameter bisects that chord. LESSON 2 - Theorem 74 - If a diameter of a circle bisects a chord of the circle which is not a diameter of the circle, then that diameter is perpendicular to that chord. Theorem 75 - If a chord of a circle is a perpendicular bisector of another chord of that circle, then the original chord must be a diameter of the circle. LESSON 3 - Theorem 76 - If two chords intersect within a circle, then the product of the lengths of the segments of one chord, is equal to the product of the lengths of the segments of the other chord. LESSON 4 - Theorem 77 - If two secant segments are drawn to a circle from a single point outside the circle, the product of the lengths of one secant segment and its external segment, is equal to the product of the lengths of the other secant segment and its external segment. Theorem 78 - If a secant segment and a tangent segment are drawn to a circle, from a single point outside the circle, then the length of that tangent segment is the mean proportional between the length of the secant segment, and the length of its external segment. LESSON 5 - Theorem 79 - If a line is perpendicular to a diameter of a circle at one of its endpoints, then the line must be tangent to the circle,at that endpoint, LESSON 6 - Theorem 80 - If two tangent segments are drawn to a circle from the same point outside the circle, then those tangent segments are congruent. LESSON 7 - Theorem 81 - If two chords of a circle are congruent, then their intercepted minor arcs are congruent. Theorem 82 - If two minor arcs of a circle are congruent, then the chords which intercept them are congruent. Part - ircles and oncurrency LESSON 1 - Theorem 83 - If you have a triangle, then that triangle is cyclic LESSON 2 - Theorem 84 - If the opposite angles of a quadrilateral are supplementary, then the quadrilateral is cyclic. Module E - Table of ontents

5 4. a) Theorem 43 - If quadrilateral is a parallelogram, then its diagonals bisect each other. b) E c) Given: Parallelogram with diagonals and intersecting at point E. d) Prove: bisects ; bisects STTEMENT RESONS 1. Parallelogram with diagonals and 1. Given intersecting at point E Theorem 41 - If a quadrilateral is a parallelogram, then both pairs of opposite sides are congruent efinition of parallelogram - a quadrilateral with both pairs of opposite sides parallel. 4. ; 4. Theorem 16 - If two parallel lines are cut by a transversal, then alternate interior angles are congruent. 5. E E 5. Postulate 13 - If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the two triangles are congruent. S ongruence ssumption) 6. E E 6. PT 7. Point E is the midpoint of 7. efinition of midpoint - a point on a line segment which is between the endpoints, and divides the given segment into two congruent parts. 8. bisects 8. efinition of bisector of a line segment - any point, line segment, ray, or line which intersects a line segment in the midpoint of the line segment, creating two congruent segments. 9. E E 9. PT 10. Point E is the midpoint of 10. efinition of midpoint 11. bisects 11. efinition of bisector of a line segment. 5. a) orollary 44 - If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram. onverse of Theorem 41) b) c) Given: Quadrilateral with and d) Prove: is a parallelogram STTEMENT RESONS 1. is a quadrilateral 1. Given 2. ; 2. Given 3. raw diagonal 3. Postulate 2 - For any two different points, there is exactly one line containing them Reflexive property for congruent line segments. 5. = 5. Postulate 13 - If three sides of one triangle are congruent to the three corresponding sides of another triangle, then the two triangles are congruent. SSS ongruence Postulate) 6. ; 6. PT 7. ; 7. Theorem 20 - If two lines are cut by a transversal so that alternate interior angles are congruent, then the two lines are parallel. 8. is a parallelogram 8. efinition of parallelogram - a quadrilateral with both pairs of opposite sides parallel Part Properties of Polygons 5

6 10. a) oth pairs of opposite sides parallel b) oth pairs of opposite sides congruent c) ny pair of consecutive angles supplementary d) Opposite angles are congruent e) iagonals bisect each other f) One pair of sides are parallel and congruent 11. a) orollary 42a - If a quadrilateral is a parallelogram, then opposite angles are congruent. b) Theorem 43 - If a quadrilateral is a parallelogram, then its diagonals bisect each other. c) Theorem 41 - If a quadrilateral is a parallelogram, then both pairs of opposite sides are congruent. d) Theorem 41 e) Theorem 42 - If a quadrilateral is a parallelogram, then any pair of consecutive angles is supplementary. f) efinition of Parallelogram - a quadrilateral with both pairs of opposite sides parallel. 12. a) 18 g) 12; 4 b) 105 h) 120 c) 12 i) 15 d) 30 j) 16 e) 115 k) 79 f) True 14. True 15. True 16. False, the quadrilateral could be a kite. 17. True 18. False, the quadrilateral could be an isosceles trapezoid. 19. Y 3,2) 7,2) 0,0) 5,0) The figure is not a parallelogram. No sides are congruent. 8 Unit V Other Polygons

7 8. a) right; congruent b) congruent; perpendicular; bisect interior c) parallelogram; rhombus; rectangle 9. a) Sometimes True f) Never True b) lways True g) Sometimes True c) lways True h) Never True d) lways True i) lways True e) Sometimes True j) Sometimes True 10. and and and E E E E 11. E E; E E 12. E; E; E; E 13. ; ; ; ; ; ; Rectangle 18. Rhombus 19. Square 20. a) U = 6 b) RU = 18 c) m GR = 70 d) m UG = a) m GR = 37 b) m GUR = a) G = U b) m UR = 45 3x + 6 = 4x = x G = 316) + 6 G = G = 54 so, G = 2 54 = 108 y y 2,5) 7,5) -1,3) 7,1) 2,1) x -5,-1) 3,-1) x -1,-5) 14 Unit V Other Polygons

8 11. is NOT a kite. and are opposite sides. 12. orollary 54a - If a quadrilateral is a kite, then the symmetry bisects and diagonal bisects the angles to which it is drawn. 13. orollary 54b - If a quadrilateral is a kite, then the symmetry bisects diagonal bisects the other diagonal. 14. orollary 54c - If a quadrilateral is a kite, then the diagonals are perpendicular to each other. 15. STTEMENT RESONS 1. is a kite with diagonals and 1. Given intersecting at point E. 2. ssume E E 2. Indirect proof assumption P..T.. 4. However, 4. efinition of Kite - quadrilateral that has two pairs of consecutive sides, but opposite sides are not congruent. 5. Our assumption that E E leads to 5. Redutio o bsurdum a contradiction of the given. So we must conclude our assumption is false and E E. 16. STTEMENT RESONS 1. is a kite. 1. Given 2. 2.Theorem 54 - If a quadrilateral is a kite, then the pair of opposite angles, formed by the two pairs of non-congruent sides are congruent. 3. ssume 3. Indirect proof assumption 4. is a parallelogram. 4. Theorem 46 - If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram. 5. or ) 5. Theorem 41 - If a quadrilateral is a parallelogram, then both pairs of opposite sides are congruent. 6. However, or ) 6. efinition of kite - a quadrilateral that has two pairs of consecutive congruent sides, but opposite sides are not congruent. 7. Our assumption that and leads to a 7. Reductio d bsurdum contradiction of the given. So we must conclude our assumption is false and. 24 Unit V Other Polygons

9 The number of sides cannot be a fraction. One angle of the regular polygon cannot measure 152 O. 34 Unit V Other Polygons

10 O 45 O 45 O E x x 45 O So, m = = 130 O Number of Sides Sum of Measures 15. Number of sides Measure of each of Interior ngles exterior angle / / ,640 The sum increases infinitely. The greatest possible sum is infinity. theoretically) The measure of each exterior angle gets smaller and smaller approaching zero. The least possible measure of an exterior angle is the smallest number greater than zero. Part Properties of Polygons 35

11 rea of Large Rectangle = b x h = 12 x 6 = 72 Square Units rea of Small Rectangle = b x h = 5 x 4 = 20 Square Units rea of Shaded Region = = 52 Square Units 14. x x x x 2 x 2 x x x 2 x 2 x x x 15. rea of Figure = = 474 Square Units rea of Shaded Region = = 314 Square Units 16. The figure on the left is 5 x 6 or 30 small squares. In terms of m, the area is 30 4 or 7 1 /2 square m s. There are 9 unshaded small squares. In terms of m, the area is 9 4 or 2 1 /4 square m s. The shaded region is 17. One square yard is 3 feet x 3 feet or 9 square feet rea of Room - b x h = 21 x 13 = 273 square feet rea of Room = = The cost would be: 18. The area of the larger lot is 4 times the area of the smaller lot. 19. rea of GEF = 1 /3 area of Example: G E 2b F b Part rea of Polygons 39

12 Part rea of Polygons 41

13 Unit V Other Polygons Part reas of Polygons p. 507 Lesson 3 Parallelogram 1. Theorem 59 - If you have a parallelogram, then the area inside the parallelogram is the product of the measures of any base and the corresponding altitude. Height Height ase ase rea = ase x Height 2. a),, F, and F are not needed. b) SU, SV, VT, TU, and SR are not needed. 3. a) b) Only one - the side parallel to the given side 4. ase is 5x or Height is 4x or 5. ltitude of parallelogram is: rea of parallelogram is: 6. ltitude of parallelogram is: rea of parallelogram is: 7. ltitude of parallelogram is: rea of parallelogram is: Part rea of Polygons 43

14 44 Unit V Other Polygons

15 Unit V Other Polygons Part reas of Polygons p. 513 Lesson 5 Regular Polygons 48 Unit V Other Polygons

16 r a S a) This is a triangle b) This is a triangle c) This is a triangle r a S a) This is a triangle b) This is a triangle c) This is a triangle Part reas of Polygons 49

17 rea of outside hexagon 3 rea of inside hexagon rea of shaded region 14. rea of pentagon rea of white triangle rea of shaded region This is a triangle. The shaded region is made up of 6 identical triangles. ltitude is where x = 12 ase is where x = 12 rea of one triangle: rea of shaded region: 50 Unit V Other Polygons

18 Unit V Other Polygons Part pplications p. 516 Lesson 1 Using reas in Proofs 1. Theorem 62 - If you have a median of a triangle, then the median separates the points inside the triangle into two polygonal regions with the same area. h Point is the midpoint of, so. 2. Theorem 63 - If you have a rhombus, then the area enclosed by that rhombus, is equal to one-half the product of the measure d1 d2 of the diagonals of the rhombus. 3. Theorem 64 - If you have two similar polygons, then the ratio of the areas of the two polygons is equal to the square of the ratio of any pair of corresponding sides. F E 4. = s 2 = s 2 Ratio of reas is = 4 2 = 8 2 = 16 units 2 = 64 units 2 Using Theorem 63: The polygons are similar. The ratio of corresponding sides is 4:8 or 1:2. The square of the ratio of corresponding sides is 1 2 :2 2 or 1:4. 5. Theorem 63: Part pplicaitons 51

19 14. The two triangles formed by extending the legs of trapezoid E are E and E. y theorem 63: 5 h2 h1 Since = 5 and = 15, we will use the ratio. 15 Find h: 15. a) b) 16. a) b) 17. a) b) The two regular octagons are similar polygons. The angles are congruent. So the ratio of a pair of corresponding angles is 1:1. Part pplications 53

20 Unit VI ircles Part Fundamental Terms p. 526 Lesson 2 rcs and ngles 1.,,, E, E nswers may vary. Here are other answers: E,, E) 2., E, E nswers may vary. Here are other answers: E,,, E) 3., E,, 4. Q, QE, Q nswers may vary. Here are other answers: QE, EQ, EQ, Q, Q) 5., E nswers may vary. Here are other answers: E, ) 6. nswers and diagrams may vary) 7. nswers and diagrams may vary) Inscribed ngle: RTU entral ngle: Q Minor rc: RU also RT and UT) Minor rc: T Q R U 8. iagrams may vary) X Q Q Y 9. a) UYV; UXV b) XQV; WQV c) WVX d) YUX; YVX R 12. a) m O = 75 b) me = 75 c) m = 20 d) OE = 5 e) me = 285 f) m OE = a) m WOZ = 34 4x + 3x + 10) + x + 2x + 10 = 360 b) mxyz = 4x + 2x + 10) = 6x + 10 = 634) + 10 = = x + 20 = x = 340 x = 34 c) m WOX = 3x + 10 = 334) + 10 = = 112 d) m YOZ = 2x + 10 = 234) + 10 = = a) or ) b) or ) c) or ) d) or ) 58 Unit VI ircles

21 15. Given: WZ is a diameter Q of Q. mwx = mxy = n Prove: m Z = n Z W Y X STTEMENT RESONS 1. WZ is a diameter of Q 1. Given 2. mwx = mxy = n 2. Given 3. m 1 = mwx = n 3. efinition of the measure of a central angle and the measure of its m 2 = mxy = n intercepted arc. 4. m 1 = m 2 4. Substitution 5. m 1 + m 2 + m 3 = straight line contains 180 O. 6. m 4 + m 5 + m 3 = Theorem 25 - If you have any given triangle, then the sum of the measures of its angles is 180 O. 7. m 1 + m 2 + m 3 = m 4 + m 5 + m 3 7. Substitution 8. m 1 + m 2 = m 4 + m 5 8. Subtraction Property of Equality 9. raw QY 9. Postulate 2 - For any two different points, there is exactly one line containing them. 10. QY QZ 10. Radii of the same circle are congruent Theorem 33 - If two sides of a triangle are congruent, then the angles opposite those sides are congruent. 12. m 4 = m efinition of ongruent ngles 13. m 1 + m 1 = m 4 + m Substitution 14. 2m 1 = 2m Properties of lgebra 15. m 1 = m Multiplication Property of Equality 16. n = m 4 or m Z) 16. Substitution Unit VI ircles Part Fundamental Terms p. 530 Lesson 3 ircle Relationships 1. One external; no internal 2. Two external; no internal 3. No external; no internal 4. No external; no internal 5. Two external; one internal 6. Two external; two internal 7. Point W is in the interior of both circles. Point X is in the exterior of the inner circle and in the interior of the outer circle. Point Y is in the exterior of the inner circle and in the interior of the outer circle. Point Z is in the exterior of both circles. 8. = E + EF + F = = Part Fundamental Terms 59

22 17. JK and PN; KT and NM TSJ and MRP; TJK and MRN 18. No. ongruent figures must have the same size in this case, length, if stretching out straight) and shape. 19. a) must b) must c) can be but need not be d) must e) cannot be f) must g) must h) can be but need not be i) must 20. infinitely many 21. infinitely many 22. yes; yes; no 23. yes; yes; no 24. l3 l2 l1 Unit VI ircles Part ngle and rc Relationships p. 534 Lesson 1 Theorem 65 and a) Theorem 65 - In a circle or in congruent circles, if two central angles are congruent, then their corresponding intercepted arcs are congruent. b) P Q c) Given: P Q; P Q d) Prove: e) STTEMENT RESONS 1. P Q 1. Given 2. P Q 2. Given 3. m P = m Q 3. efinition of ongruent ngles 4. m P = m 4. efinition of rc Measure 5. m Q = m 5. efinition of rc Measure 6. m = m 6. Substitution efinition of ongruent rcs 60 Unit VI ircles

23 6. orollary 67b - If a quadrilateral is inscribed in a circle, then its opposite angles are supplementary. x = or 95 y = or a) XZ b) NP c) d) OMQ or ONQ) e) XZ f) NP 8. a) m Y = 70 O b) m O = 40 O c) m = 55 O d) m MNQ = 40 O e) m W = 70 O f) m QPM = 40 O 9. MNQ, MOQ, MPQ 10. The angles are congruent by orollary 67c: If two inscribed angles intercept the same arc or congruent arcs, then the angles are congruent. 11. YXW, WZY 12. The angles are congruent by orollary 67c: If two inscribed angles intercept the same arc or congruent arcs, then the angles are congruent. 13. m U = 15 O, m V = 30 O, m UXV = ) O W 14. Given: WZ is a diameter of Q; QX ZY Prove: WX XY X Z 2 Q Y X STTEMENT RESONS 1. WZ is a diameter of Q 1. Given 2. QX ZY 2. Given 3. raw QY 3. Postulate 2-1st ssumption - For any two different points, there is exactly one line containing them Postulate 11 - If two parallel lines are cut by a transversal, then corresponding angles are congruent. 5. QZ QY 5. Radii of the same circle are congruent Theorem 33 - If two sides of a triangle are congruent then the angles opposite them are congruent Theorem 16 - If two parallel lines are cut by a transversal, the alternate interior angles are congruent Transitive Property of ngle ongruence 9. WX XY 9. Theorem 65 - If two central angles are congruent, then their intercepted arcs are congruent. 15. mrs + mrt + mst = 360 2x + 8) + 4x - 20) + 3x + 12) = 360 9x = 360 mrs = 2x + 8 mrt = 4x - 20 mst = 3x +12 x = 40 mrs = 240) + 8 mrt = 440) - 20 mst = 340) + 12 mrs = mrt = mrt = mrs = 88 mrt = 140 mrt = 132 Part ngle and rc Relationships 67

24 Unit VI ircles Part ngle and rc Relationships p. 544 Lesson 3 Theorem G, G 2. HG, EG F, F GF, EF E, E FE, E E F, 3. m VYW = m VYX = m WYX = m UYX = 4. a) m = b) m = c) m = d) m F = e) m = f) m = 5. a) m = b) m F = c) m EF = d) m FE = e) m F = f) m F = g) m EF = Part ngle and rc Relationships 69

25 78 Unit VI ircles

26 2. continued STTEMENT RESONS 19. is a semicircle 19. efinition of Semicircle 20. m = 180 O 20. efinition of Semicircle 21. m = m 21. Substitution 22. m + m = m + m 22. Substitution 23. m = m 23. efinition of ongruent rcs 24. m = m 24. ddition Subtraction) Property of Equality efinition of ongruent rcs 26. bisects 26. efinition of rc isector 3. If the midpoints of the two arcs of a circle determined by a chord are joined by a line segment, then the line segment is the perpendicular besector of the chord. Q E Given: and are two arcs determined by chord. Point and point are midpoints of and joined by. Prove: ; bisects STTEMENT RESONS 1. and are two arcs determined by chord. 1. Given 2. Point and point are midpoints of and 2. Given joined by efinition of midpoint efinition of midpoint 5. m = m 5. efinition of ongruent rcs 6. m = m 6. efinition of ongruent rcs 7. m + m + m + m = Postulate 8 - First ssumption - The set of all points on a circle can be put into a one-to-one correspondence with the real numbers from 0 to 360, inclusive, with the exception of any one point which may be paired with 0 and m + m + m + m = Substitution 9. 2m + 2m = Properties of lgebra - ollect like Terms 10. m + m = Multiplication Property of Equality 11. m + m = m 11. Postulate 8 - Fourth ssumption - rc ddition ssumption 12. m = Substitution 13. is a semicircle 13. efinition of Semicircle -...a semicircle is the intercepted arc of a central angle of is a diameter 14. efinition of Semicircle - n arc of a circle is a semicircle, if and only if, it is an arc whose endpoints are the endpoints of a diameter of a circle. 15. passes through point Q, the center of the circle 15. efinition of diameter 16. raw radius Q 16. Postulate 2 - For any two different points, there is exactly one line segment) containing them. 17. raw Q 17. Postulate Q Q 18. Radii of the same circle are congruent 19. m Q = m 19. efinition of Measure of a entral ngle - the measure of a minor arc and the measure of a central angle are equal. 20. m Q = m 20. efinition of Measure of a entral ngle 21. m Q = m Q 21. Substitution 22. Q Q 22. efinition of ongruent ngles 23. QE QE 23. Reflexive Property of ongruent Segments 24. QE QE 24. Postulate 13 - Triangle ongruence - If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the two triangles are congruent. SS ongruence Postulate) 25. QE QE 25..P..T QE and QE are supplementary angles 26. Theorem 10 - If the exterior sides of two adjacent angles are opposite rays, then the two angles are supplementary. 27. QE and QE are right angles 27. orollary 10b - If two angles are supplementary and congruent, then each angle is a right angle efinition of Perpendicular Lines Segments) 29. E E 29..P..T Point E is the midpoint of 30. efinition of Midpoint of a Line Segment 31. is the bisector of 31. efinition of isector of a Line Segment. Q.E.. Part Line and Segment Relationships 81

27 4. line segment is the perpendicular bisector of chord of a circle if and only if the line segment joins the midpoints of the two arcs determined by the chord. 5. PR 6. Point P 7. Point Q 8. RX 9. TY 10. XY 11. QU 12. XY 13. No 14. x = 9 Theorem x = 34 O orollary 73a ` Unit VI ircles

28 Unit VI ircles Part Line and Segment Relationships p. 560 Lesson 2 Theorem 74 & Theorem 74 - If a diameter of a circle bisects a chord that is not a diameter, then that diameter is perpendicular to that chord. Q E Given: is a diameter of Q; bisects chord Prove: STTEMENT RESONS 1. is a diameter of Q 1. Given 2. bisects chord 2. Given 3. Point E is the midpoint of 3. efinition of Line Segment isector 4. E E 4. efinition of Midpoint 5. QE QE 5. Reflexive Property for ongruent Line Segments 6. raw Q 6. Postulate 2 - For any two different points, there is exactly one line segment) containing them. 7. raw Q 7. Postulate 2 8. Q Q 8. Radii of the same circle are congruent 9. QE QE 9. Postulate 13 - Triangle ongruence - If the three sides of one triangle are congruent to the three sides of another triangle, then the two triangles are congruent. SSS ongruence ssumption) 10. QE QE 10..P..T orollary 10d - If two congruent angles form a linear pair, then the intersecting lines forming the angles are perpendicular. 2. Theorem 75 - If a chord of a circle is a perpendicular bisector of another chord of that circle, then the original chord must be a diameter of the circle. X Given: hord bisects chord at point X. Prove: is a diameter of the circle. Q STTEMENT RESONS 1. hord bisects chord at point X 1. Given Given 3. ssume is not a diameter of Q 3. Indirect Proof ssumption 4. There must exist a chord EF through point Q, the 4. Postulate 2 - For any two different points, there is exactly one line center of the circle, and point X, the midpoint of containing them. chord 5. EF is a diameter 5. efinition of iameter - line segment which is a chord of a circle, and passes through the center of that circle. 6. EF 6. Theorem 74 - If a diameter of a circle bisects a chord that is not a diameter, then that diameter is perpendicular to that chord. 7. However, at point X 7. Given 8. EF and cannot both be perpendicular to 8. Theorem 6 - If, in a plane, there is a point on a line, then there is at point X exactly one perpendicular to the line through that point. 9. Our ssumption must be false. 9. Reductio d bsurdum must be a diameter = 18 Theorem 75 If a chord ) of a circle is a perpendicular bisector of another chord MN) of that circle, then the original chord must be a diameter of the circle. Part Line and Segment Relationships 83

29 15. Given: is a diameter of Q bisects ; bisects EF Prove: EF E Y X Q F STTEMENT RESONS 1. is a diameter of Q 1. Given 2. bisects 2. Given Theorem 74 - If a diameter of a circle bisects a chord that is not a diameter, then that diameter is perpendicular to that chord. 4. bisects EF 4. Given 5. EF 5. Theorem EF 6. Theorem 22 - If two lines are perpendicular to a third line, then the two lines are parallel. 16. Two chords of a circle that are not diameters are parallel to each other if and only if a diameter of the circle bisects the two chords. 17. Proof of Theorem 75 STTEMENT RESONS 1. hord bisects chord at point E 1. Given 2. Point E is the midpoint of 2. efinition of Line Segment isector 3. E E at point E 3. efinition of Midpoint Given 5. E is a right angle 5. efinition of Perpendicular Lines Segments) 6. E is a right angle 6. efinition of Perpendicular Lines Segments) 7. E E 7. Theorem 11 - If you have right angles, then those right angles are congruent. 8. E E 8. Reflexive Property for ongruent Line Segments 9. raw 9. Postulate 2 - For any two different points, there is exactly one line segment) containing them. 10. raw 10. Postulate E E 11. Postulate 13 - Triangle ongruence - If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle then the two triangles are congruent. SS ongruence ssumption) P..T m = 1 m 13. Theorem 67 - If you have an inscribed angle of a circle, then the 2 measure of the angle is one-half the measure of the intercepted arc. 14. m = 1 m 14. Theorem m = m 15. efinition of ongruent ngles m = 1 m 16. Substitution m = m 17. Multiplication Property of Equality P..T m = 1 m 19. Theorem m = 1 m 20. Theorem m = m 21. efinition of ongruent ngles m = 1 m 22. Substitution m = m 23. Multiplication Property of Equality 24. m + m + m + m = Postulate 8 - First ssumption - The set of all points on a circle can be put into a one-to-one correspondence with the real numbers from 0 to 360, inclusive, with the exception of any one point which may be paired with 0 and m + m + m + m = Substitution 26. 2m + 2m = Properties of lgebra - ollect Like Terms 27. m + m = Multiplication Property of Equality 28. m + m = m 28. Postulate 8 - Fourth ssumption - rc ddition ssumption 29. m = Substitution 30. is a semicircle 30. efinition of Semicircle -...a semicircle is the intercepted arc of a central angle of 180 O 31. is a diameter of the circle 31. efinition of Semicircle - n arc of a circle is a semicircle, if and only if, it is an arc whose endpoints are the endpoints of a diameter of a circle. Part Line and Segment Relationships 85

30 Unit VI ircles Part Line and Segment Relationships p. 568 Lesson 4 Theorem 77 & Theorem 77 - If two secant segments are drawn to a circle from a single point outside the circle, the product of the lengths of one secant segment and its external segment, is equal to the product of the lengths of the other secant segment and its external segment. Q P Given: P and P are secants of Q. Prove: P P = P P STTEMENT RESONS 1. P and P are secants of Q 1. Given 2. raw 2. Postulate 2 - For any two different points, there is exactly one line segment) containing them. 3. raw 3. Postulate orollary 67c - If two inscribed angles intercept the same arc or congruent arcs, then the angles are congruent. 5. P P 5. Reflexive Property of ngle ongruence 6. P ~ P 6. Postulate orollary 12a - If two angles of one triangle are congruent to the two corresponding angles of another triangle, then the two triangles are similar. ) efinition of Similarity - Two polygons are similar if and only if corresponding angles are congruent and corresponding sides are in proportion. 8. P P = P P 8. Multiplication Property of Equality Multiply both sides by P P) 2. Theorem 78 - If a secant segment and a tangent segment are drawn to a circle from a single point outside the circle, then the length of the tangent segment is the mean proportional between the length of the secant segment and its external segment. Q P Given: P is a secant segment of Q. P is a tangent segment to Q. Prove: P mean proportional between P and P.) STTEMENT RESONS 1. P is a secant segment of Q. 1. Given 2. P is a tangent segment to Q. 2. Given 3. raw chord 3. Postulate 2 - For any two different points, there is exactly one line segment) containing them. 4. raw chord 4. Postulate m P = m 5. Theorem 68 - If you have an angle formed by a secant and a tangent 2 at the point of tangency, then the measure of that angle is one-half the measure of its intercepted arc m P = m 6. Theorem 67 - If an angle is inscribed in a circle, then the measure of 2 that angle is one-half the measure of the intercepted arc. 7. m P = m P 7. Substitution 8. P P 8. efinition of ongruent ngles 9. P P 9. Reflexive Property for ongruent ngles 10. P ~ P 10. Postulate orollary 12a - If two angles of one triangle are congruent to the two corresponding angles of another triangle, then the two triangles are similar. ) efinition of Similarity - Two polygons are similar if and only if corresponding angles are congruent and corresponding sides are in proportion. 12. P is the mean proportional between P and P 12. efinition of Mean Proportional 88 Unit VI ircles

31 Unit VI ircles Part Line and Segment Relationships p. 571 Lesson 5 Theorem Theorem 79 - If a line is perpendicular to a diameter of a circle at one of its endpoints, then the line is tangent to the circle at that endpoint. Q Given: Q with diameter. at point Prove: is tangent to Q. E l1 STTEMENT RESONS 1. Q with diameter 1. Given 2. at point 2. Given 3. hoose any point E on and draw QE. 3. Postulate 2 - For any two different points, there is exactly one line segment) containing them. 4. Q < QE 4. segment is the shortest segment from a point to a line if and only it it is the segment perpendicular to the line. 5. Point E lies in the exterior of Q 5. If a point is in the exterior of a circle, then the measure of the segment joining the point to the center of the circle is greater than the measure of the radius. 6. is tangent to Q at point 6. efinition of Tangent 2. Theorem 79 - If a line is perpendicular to a diameter of a circle at one of its endpoints, then the line is tangent to the circle at that endpoint. Given: Line m is perpendicular to P at point. Prove: Line m is tangent to Q. Proof: Let point be any point on line m other than point. SInce P m, Q is a right triangle with hypotenuse Q. This means Q > Q and point must be in the exterior of Q. Therefore, point cannot lie on the circle and point is the only point on line m that is on the circle. It follows that line m is tangent to the circle degrees 4. Tangent; Theorem 79 - If a line is perpendicular to a diameter of a circle at one of its endpoints, then the line is tangent to the circle at that endpoint degrees Unit VI ircles

32 9. 48 degrees 10. Tangent; Theorem 79 - If a line is perpendicular to a diameter of a circle at one of its endpoints, then the line is tangent to the circle at that endpoint degrees P; Q Theorem 79 - If a line is perpendicular to a diameter of a circle at one of its endpoints, then the line is tangent to the circle at that endpoint. 16. In the plane of Q, the line m is tangent to Q at point, if and only if, the line m is perpendicular to diameter P at point. Part Line and Segment Relationships 93

33 5. PX PY Theorem 80) PYX is isosceles by definition of an isosceles triangle two sides are congruent). PYZ PXY Theorem 33) QY PY orollary 68a) QYP is a right angle, so m QYP = 90. SInce m XYQ = 10 degrees, m XYP = 80 degrees = 80) The sum of the measures of the angles of a triangle is 180. Q X Y P m XYP + m YXP + m P = m P = m P = 180 m P = Label the points of tangency W, X, Y, and Z. Part 1: W = Z, W = X, X = Y and Y = Z Theorem 80) = W + W and = Y + Y. + = W + W + Y + Y Z W Q X Part 2: = Z + Z and = X + X + = Z + Z + X + X Substituting W for Z, W for X, Y for Z, and Y for X, we have + = W + Y + W + Y Using the ommutative Property for ddition, we have + = W + W + Y + Y Therefore, + = + Y 7. RX = RZ and TY = TZ Theorem 80) PX = PR + RX PY = PT + TY PX + PY = PR + RX + PT + TY RT = RZ + TZ RT = RX +TY Substituting RX for RZ and TY for TZ) Since PX + PY = PR + RX + TY + PT Using the ommutative Property of ddition) we can substitute RT for RX +TY to get PX + PY = PR + RT + PT 8. Q and Q orollary 68a) Q and Q are right angles. m Q = m Q = 90 m Q + m Q + y = y = y = 180 y = 10 Therefore, W = 10 orollary 80a) m Q + w + z = z = z = 180 z = 80 m Q = = 100) x = 100 measure of an arc is the same as the measure of its central angle) 96 Unit VI ircles

34 Unit VI ircles Part ircles oncurrency l1 p. 581 Lesson 1 Theorem Given: ; is a chord of some circle Prove: is cyclic Q P M N l2 STTEMENT RESONS Given 2. is a chord of some circle. 2. Given 3. Locate point M on as the midpoint of. 3. Theorem 4 - If you have a given line segment, then that segment has exactly one midpoint. 4. raw l 1 perpendicular to at point M. 4. Theorem 6 - If, in a plane, there is a point on a line, then there is exactly one perpendicular to the line through that point. 5. l 1 contains a diameter of the circle which has 5. Theorem 75 - If a chord of a circle l 1 ) is a perpendicular bisector of as a chord. another chord ) of that circle, then the original chord l 1 ) must be a diameter of the circle must pass through the center of the circle. 6. efinition of iameter 7. Locate point N on as the midpoint of. 7. Theorem 4 8. raw l 2 perpendicular to at point N. 8. Theorem 6 9. all the intersection of l 1 and l 2 point P. 9. Postulate 5 - If two different lines intersect, the intersection is a unique point. 10. raw P. 10. Postulate 2 - For any two different points, there is exactly one line segment) containing them. 11. raw P. 11. Postulate raw P. 12. Postulate PM is a right angle. 13. efinition of Perpendicular Lines 14. PM is a right triangle. 14. efinition of Right Triangle 15. PM is a right angle. 15. efinition of Perpendicular Lines 16. PM is a right triangle. 16. efinition of Right Triangle 17. M M 17. efinition of Midpoint of a Line Segment 18. PM PM 18. Reflexive Property for ongruent Line Segments 19. PM PM 19. Postulate orollary 13b - If the two legs of a right triangle are congruent to the two legs of another right triangle, then the two right triangles are congruent. LL) 20. P P 20..P..T PN is a right angle. 21. efinition of Perpendicular Lines 22. PN is a right triangle. 22. efinition of Right Triangle 23. N N 23. efinition of Midpoint of a Line Segment 24. PN PN 24. Reflexive Property for ongruent Line Segments 25. PN = PN 25. Postulate orollary 13b 26. P P 26..P..T P = P 27. efinition of ongruent Line Segments 28. P = P 28. efinition of ongruent Line Segments 29. P = P = P 29. Transitive Property of Equality 30. is cyclic. 30. Using P, P and P as radii, draw a circle with point P as the center passing through points, and. Q.E..) 104 Unit VI ircles

35 M = M orollary 83a) Since MP bisects and = P + P, then = = lways 17. lways 18. Never 19. Sometimes 20. lways Recall theorem 67. So, the right angle must intercept a semicircle. This leads to the hypotenuse being the diameter of the circle.) = The midpoint of a line segment is given by: The midpoint of : The midpoint of : The midpoint of : Slope of : Slope of line perpendicular to : Undefined Slope of : Slope of line perpendicular to : Slope of : Slope of line perpendicular to : Part ircles oncurrency 111

36 10. The inscribed square is a rhombus, so diagonal bisects. m = 90, so m = 45. EQ is therefore a triangle. Let E and QE equal x. Q is then. 11. a) 120 b) 90 c) 60 d) STTEMENT RESONS 1. Quadrilateral XYWZ is cyclic. 1. Given 2. ZY is a diameter of Q. 2. Given 3. XY II ZW 3. Given 4. XYZ WZY 4. Theorem 16 - If two parallel lines are cut by a transversal, then alternate interior angles are conruent. 5. ZXY is a right angle. 5. orollary 67a - If you have an angle inscribed in a semicircle, then that angle must be a right angle. 6. ZXY is a right triangle. 6. efinition of Right Triangle 7. YWZ is a right angle. 7. orollary 67a 8. YWZ is a right triangle. 8. efinition of Right Triangle 9. ZXY YWZ 9. Postulate orollary 13e - If the hypotenuse and an acute angle of one right triangle are congruent to the hypotenuse and an acute angle of another right triangle, then the two right triangles are congruent. H) 10. XZ WY 10..P..T XZ WY 11. Theorem 81 - If two chords of a circle are congruent, then their minor arcs are congruent. 12. XY WZ 12..P..T XY WZ 13. Theorem 81 - If two chords of a circle are congruent, then their minor arcs are congruent. 13. a) m Q = 90 b) c) istance from point Q to 116 Unit VI ircles