1. 6.1(a) Notes: Triangle Angle-Sum Theorem
Lesson Objective: Apply the Triangle Angle-Sum Theorem
CCSS: G.CO.10 Prove theorems about triangles
You will need: colored pens, PR
Real-World App: What are the angles of a soccer kicking activity?
This is Jeopardy!!!:  

2. Lesson 1: Triangle Sum Theorem
Label your loose triangle as shown. Trace the triangle onto your paper using a blue line for the base. Label the angles on your paper. 2
Why is the sum of the angles of a triangle = 180°?

3. Lesson 1: Triangle Sum Theorem
Tear off the corners of angles 1 and 3 of the loose triangle. Tear off enough that you can hold them easily. 2
Why is the sum of the angles of a triangle = 180°?

4. 1 3 Lesson 1: Triangle Sum Theorem
Rotate pieces 1 and 3 180° and place on each side of angle 2. Glue everything down. 2 1 3

5. Lesson 1: Triangle Sum Theorem Draw a line along the three angles.
Draw a line along the three angles.

6. Lesson 1: Triangle Angle-Sum Theorem
180°
Example: m/ 1 + m/ 2 + m/ 3 = 180°
A straight line = 180°. The sum of the angles of a triangle = a straight line = 180°.

7. Lesson 2: Using the Triangle Angle-Sum Theorem with Mrs. Highman
SOCCER The diagram shows the path of the ball in a passing drill between 4 friends. Find the measures of each numbered angle.

8. Lesson 3: Using Variables and the Triangle Angle-Sum Theorem
Find the measures of each angle. a.

9. Lesson 3: Using the Triangle Angle-Sum Theorem
Find the measures of each numbered angle. b.

10. 6.1(a): Do I Get It? Yes or No
Find the measures of each numbered angle. 1.

11. 6.1(a): Do I Get It? Continued
2. Find the measures of each numbered angle. 2.