Exterior Angles of Triangles
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Objective
I can apply the exterior angle theorem to solve for unknown angles in triangles.
Part 1 of 3
Key concepts
3 concepts
- 1
An exterior angle is formed when one side of a triangle is extended beyond its vertex.
- 2
The exterior angle theorem states that the measure of an exterior angle is equal to the sum of the two non-adjacent interior angles.
- 3
If ∠ACD is an exterior angle of triangle ABC, then ∠ACD = ∠A + ∠B.
Part 2 of 3
Practice
7 questions
Define an exterior angle of a triangle.
State the exterior angle theorem.
Part 3 of 3
Exit ticket
Quick comprehension check
“In triangle PQR, side QR is extended to point S, forming exterior angle ∠PRS. If ∠P = 58° and ∠Q = 73°, find the measure of ∠PRS.”
Sample answer included in the free materials
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