1. 6.1(b) Notes: Exterior Angle Theorem
Lesson Objective: Apply Exterior Angle Theorem
CCSS: G.CO.10 Prove theorems about triangles
You will need: a pencil, colored pens
Real-World App: What is the angle that a bracket makes with a wall?
This is Jeopardy!!!: This is the m/ A when m/ B = 42° A
B C

2. Lesson 1: Exterior Angle Theorem
Draw a line across the page, starting at the left margin.

3. Lesson 1: Exterior Angle Theorem
Label your loose triangle as shown. Trace the triangle onto your page. Label. Tear off angles 1 and 2 of the loose triangle. 2   
Exterior Angle Theorem:

4. Lesson 1: Exterior Angle Theorem
Glue your triangle down on to the line. Label the exterior angle / 4 far off the angle as shown.     

5. 2 Lesson 1: Exterior Angle Theorem
Place / 1 and / 2 inside exterior / 4 as shown and glue them What do you observe?   
Exterior Angle Theorem: 2

6. 2 Lesson 1: Exterior Angle Theorem
Example: m/ 4 = m/ 1 + m/ 2
Exterior
Remote
   Interior
Exterior Angle Theorem:
The measure of the exterior angle = the sum of the remote interior angles. 2

7. Lesson 2: Using the Exterior Angle Theorem

8. Lesson 2: Using the Exterior Angle Theorem
FITNESS Find the measure of / JKL in the Triangle Pose shown.

10. Lesson 3: Finding Angle Measures in Right Triangles
Find m/ 1.
Find m/ 2.
Find m/ 3.
Find m/ 4.

11. 6.1(b): Do I Get It? Yes or No
1. Find m/ 1 on the truck 2. Find the value
below. Then find m/ 2. of x in the figure
below. Then find the
measure of each
angle.