Interactive resource
Exterior angle of a triangle
Geometry. See that an exterior angle equals the sum of the two remote interior angles. Free interactive GeoGebra resource — adjust parameters in the browser.
Overview
See that an exterior angle equals the sum of the two remote interior angles.
Explanation
An exterior angle equals the sum of the two non-adjacent interior angles.
It also equals 180° minus the adjacent interior angle.
Corollary: an exterior angle is greater than either remote interior angle.
How to use
Drag vertices and compare exterior ∠ACD with ∠A + ∠B.