= Exterior angle theorem
{wiki=Exterior_angle_theorem}
The Exterior Angle Theorem is a fundamental principle in triangle geometry that relates the measures of an exterior angle of a triangle to the measures of its remote interior angles. The theorem states that: In any triangle, the measure of an exterior angle is equal to the sum of the measures of the two opposite (or remote) interior angles. To illustrate, consider triangle ABC where angle C is an exterior angle formed by extending side AC.
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