Triangle Angle Sum: The Easy Check Students Forget

Updated Aug 30, 2026 · View standard page

The interior angles of any triangle add to 180°.

If two angles are 48° and 67°, the third is:

180 − 48 − 67 = 65°

With algebra

If a triangle has angles x, x and 50°, then:

x + x + 50 = 180 2x = 130
x = 65

So the angles are 65°, 65° and 50°.

Final check: add your three angles. If they do not total 180°, revisit the working.