1. Geometry Section 4.1 Apply Triangle Sum Properties

3. Angles of a Triangle When the sides of a polygon (triangle) are extended, other angles are formed. The original angles are the interior angles. The angles that form linear pairs with the interior angles are the exterior angles

5. Triangle Sum Theorem The sum of the measures of the interior angles is 180° A B C

6. Exterior Angle Theorem The measure of an exterior triangle is equal to the sum of the measures of the two nonadjacent interior angles A B C 1

7. Corollary to the Triangle Sum Theorem The acute angles of a right triangle are complementary A BC

8. Examples Page 221 #15, 17, 33, 37

9. Assignment Section 4.1 Page 221 Problems #1-6 all, 8-18 even, 21-26, 32, 34