Supplementary Angles

Definition: Two angles that add up to 180°
Try this Drag an orange dot. The two angles will change so that they always add to 180°

In the figure above, the two angles PQR and JKL are supplementary because they always add to 180°

Often the two angles are adjacent, in which case they form a linear pair like this:

linear pair of angles - two angles that are adjacent (share a leg) and supplementary (add up to 180 deg)

Similar in concept are complementary angles, which add up to 90°.

A way to remember

Sometimes it's hard to remember which is which between supplementary (adds to 180°) and complementary (adds to 90°). Here are two memory aids:

Other angle topics


Angle Types

Angle relationships