1. Bellwork Classify each angle as acute, obtuse, or right. 90° 72° 116°
How do you know that ? 1 2

2. Apply Triangle Sum Properites
Lesson 4.1
Apply Triangle Sum Properites

3. Objective
Students classify triangles and find measures of their angles.

4. Standard
12.0 – Students find and use measures of sides and of interior and exterior angles of triangles and polygons to classify figures and solve problems
13.0 – Students prove relationships between angles in polygons by using properties of complementary, supplementary, vertical, and exterior angles.

5. Academic Language Triangles Interior angles Exterior angles
Scalene, isosceles, equilateral, acute, right, obtuse, equiangular
Interior angles
Exterior angles
Corollary to a theorem

6. Think/Pair/Share
Right, obtuse, acute, equilateral, isosceles, and equiangular

7. Triangle
Polygon with 3 sides A B C

10. The Real World!

11. Practice

12. Interior vs. Exterior……….Angles

14. Prove

16. Example

17. Homework
p.221 #1 – 7, 10, 15, 19, 21 – 26, 29