1. Angles of Triangles LESSON 4–2

2. Over Lesson 4–1 5-Minute Check 1 A.acute B.equiangular C.obtuse D.right Classify ΔRST.

3. Over Lesson 4–1 5-Minute Check 2 A.8 B.10 C.12 D.14 Find y if ΔRST is an isosceles triangle with RS  RT. ___

4. Over Lesson 4–1 5-Minute Check 3 A.2 B.4 C.6 D.8 Find x if ΔABC is an equilateral triangle.

5. Over Lesson 4–1 5-Minute Check 4 A.ΔABC B.ΔACB C.ΔADC D.ΔCAB

6. Over Lesson 4–1 5-Minute Check 5 A.scalene B.isosceles C.equilateral Classify ΔMNO as scalene, isosceles, or equilateral if MN = 12, NO = 9, and MO = 15.

7. Over Lesson 4–1 5-Minute Check 6 A.acute B.scalene C.isosceles D.equiangular Which is not a classification for ΔFGH?

8. Then/Now You classified triangles by their side or angle measures. Apply the Triangle Angle-Sum Theorem. Apply the Exterior Angle Theorem.

9. Vocabulary auxiliary line exterior angle remote interior angles flow proof corollary

10. Concept 1

11. Concept 2

12. Example 1 Use the Triangle Angle-Sum Theorem SOFTBALL The diagram shows the path of the softball in a drill developed by four players. Find the measure of each numbered angle.

13. Example 1 A.95 B.75 C.57 D.85 Find the measure of  3.

14. Concept 3

15. Concept 4

16. Example 2 Use the Exterior Angle Theorem GARDENING Find the measure of  FLW in the fenced flower garden shown. Answer: So, m  FLW = 2(80) – 48 or 112.

17. Example 2 A.30 B.40 C.50 D.130 The piece of quilt fabric is in the shape of a right triangle. Find the measure of  ACD.

18. Concept 5

19. Example 3 Find Angle Measures in Right Triangles Find the measure of each numbered angle. m  1 = 70, m  2 = 110, m  3 = 46, m  4 = 102, m  5 =37

20. Example 3 A.50 B.45 C.85 D.130 Find m  3.

21. Angles of Triangles LESSON 4–2