1. 4.1 Triangles and Angles Pg 194

2. Triangles Triangle-figure formed by 3 segments joining 3 noncollinear pts. Triangles are named by these three pts (ΔQRS) Q R S

3. Classifying Δs by Angles or Sides Angles Acute Obtuse Right Equiangular Sides Scalene Isosceles Equilateral

4. Each of the three points are vertices Adjacent sides- 2 sides sharing a common vertex Third side is opposite the given vertex. A B C

5. Parts of a Right Triangle Leg Hypotenuse

6. Parts of an Isosceles Triangle Leg Base __ ___

7. How can ΔABC be right and isosceles? A B C ____ _____

8. Interior Angles )) ))) ( A B C

9. Exterior Angles (formed by extending the sides) ( )) (( D E F An exterior angle and its corresponding interior angle add up to 180 ⁰.

10. How do we measure an angle with a protractor?

11. Thm 4.1:Triangle Sum Thm The sum of the measures of the interior angles of a triangle is 180 o. m  A + m  B+ m  C=180 o A BC

12. Thm 4.2: Exterior Angles Thm The measure of an exterior angle of a triangle is equal to the sum of the measures of the 2 nonadjacent interior angles. m  1=m  A+ m  B 1 A B C

13. Corollary to triangle sum thm (Corollary- a statement easily proved using a thm.) * The acute angles of a right triangle are complementary. A B C  A is comp. to  C

14. Assignment Geometry Textbook p. 198-199 (1-9, 31-39)