Chapter 1 — Answers
Selected answers for Chapter 1: An Introduction to Geometry, transcribed from the book’s appendix. They are meant for checking your work, not for copying — the book prints answers to selected exercises only.
Back to Chapter 1 · Teacher’s answers: Chapter 1 · Complete key: Answers to Exercises PDF · Printed answers: appendices PDF
Lesson 1 (pages 10–11)
2. 12 cm.
5. About 1.3 cm.
7. 3 mi.
14. Line segments.
21. Three.
25. Six; AB, AG, AC, AF, AD, AI.
Lesson 2 (pages 15–17)
2. ∠C.
6. Rays AC and AB.
10. ∠B = 30°.
13. Collinear.
16. ∠1 = 67°.
22. ∠I = 117°.
25. Approximately ft.
28. Approximately ft.
30. 34°.
Lesson 3 (pages 21–22)
2. 9 in².
3. 12 in.
4. 36 in².
5. 24 in.
13. Piece I because it has four sides.
16. Ranch A.
23. Polygons.
25. Eight.
28. Three.
30. A line.
32. 75.6 ft.
Lesson 4 (pages 26–29)
5. Noncollinear.
11. The bisecting lines seem to be concurrent.
16. No.
17. West.
21. About 6 A.M. and 6 P.M.
23. OI bisects ∠HOJ.
25. ∠DOB and ∠EOA.
31. 60°.
33. 180°.
Lesson 5 (pages 31–34)
1. 100 square units.
6. It contains 80 square units.
8. 54 square units.
11. It contains 84 square units.
Review (pages 36–38)
2. Polygons (or squares).
5. 12.
8. Coplanar.
10. PQ.
13. T.
18. Constructions.
20. ∠DAB = 110°.
25. ∠DCF = ∠FCE = 40°.
Algebra Review (page 40)
1. Associative for addition.
2. Commutative for multiplication.
3. Definition of subtraction.
4. Identity for addition.
5. Definition of division.
6. Inverse for multiplication.
7. 1,728.
8. 12,000.
9. 20.
10. −75.
11. 225.
12. 81.
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