1. Do Now Classify the following triangles as acute, right, or obtuse. 2.3. 1. 2.

2. Section 4.1 – Apply Triangle Sum Properties
Objective: SWBAT classify triangles and find the measures of their angles.

3. A triangle is a polygon with three sides
A triangle is a polygon with three sides. A triangle with vertices A, B, and C is called “triangle ABC”.

4. Apply Triangle Sum Properties
When the sides of a polygon 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.

6. Example 3: Find an angle measure. Find m<JKM

7. Example 4: Find an angle measure. Find m<DEF

8. A corollary to a theorem is a statement that can be proved easily using the theorem.

9. Example 5:
The support for a skateboard ramp shown forms a right triangle. The measure of one acute angle in the triangle is five times the measure of the other. Find the measure of each acute angle.

10. Classwork/Homework
Complete ALL problems on Triangle Sum and Exterior Angle Theorem Worksheet