Exterior Angles of Triangles

An exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side.
Try this Drag the orange dots on any vertex to reshape the triangle. One of the six possible exterior angles is shown. Note how it changes.


Other triangle topics


Perimeter / Area

Triangle types

Triangle centers

Congruence and Similarity

Solving triangles

Triangle quizzes and exercises