1. Splash Screen

2. Lesson Menu Five-Minute Check (over Lesson 4–1) Then/Now New Vocabulary Theorem 4.1: Triangle Angle-Sum Theorem Proof: Triangle Angle-Sum Theorem Example 1: Real-World Example: Use the Triangle Angle-Sum Theorem Theorem 4.2: Exterior Angle Theorem Proof: Exterior Angle Theorem Example 2: Real-World Example: Use the Exterior Angle Theorem Corollaries: Triangle Angle-Sum Corollaries Example 3: Find Angle Measures in Right Triangles

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

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

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

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

7. Over Lesson 4–1 1.A 2.B 3.C 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.

8. Over Lesson 4–1 1.A 2.B 3.C 4.D 5-Minute Check 6 A.acute B.scalene C.isosceles D.equiangular Which is not a classification for ΔFGH?

9. Then/Now You classified triangles by their side or angle measures. (Lesson 4–1) Apply the Triangle Angle-Sum Theorem. Apply the Exterior Angle Theorem.

10. Vocabulary auxiliary line exterior angle remote interior angles

11. Concept 1

12. Concept 2

13. 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.

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

15. Concept 3

16. Concept 4

17. Example 2 Use the Exterior Angle Theorem GARDENING Find the measure of  FLW in the fenced flower garden shown.

18. A.A B.B C.C D.D 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.

19. Concept 5

20. Example 3 Find Angle Measures in Right Triangles Find the measure of each numbered angle. m  1 = 104, m  2 = 76, m  3 = 42, m  4 = 48, m  5 = 49

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

22. End of the Lesson