Interior Angles of Triangles
Grade 9th Grade · Math · 45 min
What's Included
Learning Objective
I can prove that the sum of the interior angles of a triangle is 180 degrees.
Warm-Up Video
Kristen Watson · 4:24
Triangle Sum Theorem
Guided Notes
3 key concepts
- 1
The Triangle Sum Theorem states that the sum of the three interior angles of any triangle will always add up to 180 degrees.
- 2
If a triangle has angles A, B, and C, then the equation A + B + C = 180 can be used to solve for missing angle measurements.
- 3
When solving for a variable within angle expressions, remember to combine like terms before isolating the variable using inverse operations.
Practice Questions
10 questions · Multiple choice & Short answer
Exit Ticket
Quick comprehension check
“In triangle ABC, ∠A measures 60°, ∠B measures 80°. What is the measure of ∠C?”
Complete Lesson Package
Get all 3 ready-to-use resources:
Teacher Guide
Student Doc
Slides
