1. Applying Angle Theorems
DRAW
Exterior Angle Sums Theorem
Error Analysis

2. Instructions for The Triangle Problem (1).
“This triangle has missing angle measures. Students have solved the problems in different ways and explained their work. Only 1 of the 4 problems presented is correct. The other 3 examples have measures for the angles that are wrong.
Solve for the measure of the exterior angle marked and explain your reasoning. On your answer sheet, tell what each student did wrong and correctly solve the problem..”   

3. Instructions for The Triangle Problem (2)
Four students in Mrs. McNeil’s class came up with different methods for answering this problem.
Their methods are shown on the worksheets around the room.
Use each student’s method to calculate the measure of the exterior angle.
Choose which student is correct and write your reasoning in detail for each of the 4 methods. Are they wrong? Why? What did they forget to do? (Step 1, then, lastly…)

4. Instructions for Sample Responses to Discuss
Four students, Annabel, Carlos, Brian and Megan answered The Triangle Problem using different methods.
For each piece of work:
Explain whether the student’s reasoning is correct and complete.
Correct the solution if necessary.
Use the method to calculate the final measure of exterior angle.
Make sure to write down all your reasoning in detail.

5. Annabel’s method

6. Carlos’s method

7. Brian’s method

8. Megan’s method

9. Applying Angle Theorems
Who’s right?
Prove it!!!
What did they do wrong?
How do you know??