LearningDemonstratesv1

The angles of a triangle sum to 180 degrees

A parallel-line construction reveals the angle sum.

Output

Three adjacent angles forming 180 degrees

Input

Any triangle on a flat plane

Input

Any triangle on a flat plane

Three adjacent angles forming 180 degrees

Relationship

Draw a line through one vertex parallel to the opposite side. Alternate interior angles place all three triangle angles along one straight line.

mathworld.wolfram.com: The angles of a triangle sum to 180 degreesmathworld.wolfram.com