1. Warm ups Classify ΔRST. Find y if ΔRST is an isosceles triangle with RS = RT. ___ Find x if ΔABC is an equilateral triangle.

2. 4-2 ANGLES OF TRIANGLES

3. Triangle Angle-Sum Theorem

4. Example SOFTBALL The diagram shows the path of the softball in a drill developed by four players. Find the measure of each numbered angle. Plan:You know that <1 and <2 are vertical angles. Use the Ver. Angles Thm to find m<2. Then you will have enough information to find the measure of <3.

5. Example Plan***Find m<1 first because the measure of two angles of the triangle are known. So, m<2 = 63. Therefore, m<1 = 63, m<2 = 63, and m<3 = 38.

6. TWAP A.95 B.75 C.57 D.85 Find the measure of  3.

7. Exterior Angle Theorem

8. Example Find the measure of <FLW. m<LOW + m<OWL = m<FLW Exterior Angle Thm x + 32= 2x – 48 32= x – 48 80= x Answer: So, m<FLW = 2(80) – 48 = 112.

9. TWAP 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.

10. Corollary – statement that can be easily proved using a theorem

11. Example Find the measure of each numbered angle. Exterior Angle Theorem M<1 = 48 + 56 = 104 104 + m<2 = 180 76

12. Example continued 48 132 + m<4 = 180 56 + 76 + m< 4 = 180 56 + m<2 + m< 4 = 180 = 42 M< 3 = 90 – 48 Bottom angle: 90-34 = 56

13. Example cont 49 m<5 + 143 = 180 m<5 + 41 + 90 = 180 m<1 = 104, m<2 = 76, m<3 = 42, m<4 = 48, m<5 = 49 That was a CRAZY one!!!!!!!!!!!

14. TWAP A.50 B.45 C.85 D.130 Find m<3.

15. Homework Pg. 250 #11-32 all, 46, 50