Home/Eighth Grade Math/Week 29: Triangles/Lesson 5

Triangle Angle-Sum Theorem

Interior angles of any triangle add to 180 degrees.

Lesson 5

Concept

For triangle ABC: m<A + m<B + m<C = 180° Examples: - If two angles are 50° and 60°, third is 70°. - If angles are (x+20), (2x), and (x+10): (x+20) + 2x + (x+10) = 180 4x + 30 = 180 4x = 150 x = 37.5

Try it

Practice: Triangle Angle-Sum Theorem.