# How are the interior and exterior angles of a triangle related?

How are the interior and exterior angles of a triangle related?
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Nola Robson
By the Exterior Angle Theorem, the measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior angles (the angles that do not form a linear pair with the exterior angle).
Consider $\mathrm{△}ABC$ below:
The exterior angle measures $m\mathrm{\angle }ACD=110\circ$ and the two remote interior angles have a sum of $m\mathrm{\angle }A+m\mathrm{\angle }B=60\circ +50\circ =110\circ$. Therefore $m\mathrm{\angle }ACD=m\mathrm{\angle }A+m\mathrm{\angle }B$.