Find 3rd Angle of Triangle

Find Unknown Angles: Learn

The sum of the interior angles of a triangle are equal to 180°. That is, all 3 of the angles in a triangle should add up to 180°.

When two angle are known but the third is unknown, we can calculate the unknown angle. To find the third unknown angle of a triangle, subtract the number of degrees in the other two angles from 180°.

Example: How many degrees are in the third angle of a triange whose other two angles are 40° and 65°?

Answer: 180° - 40° - 65° = 75°

Find Unknown Angles: Practice


What is the unknown angle of a triangle whose known angles are
° and °?


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