What are supplementary angles?

Supplementary angles are defined as two angles whose measures add up to 180 degrees. This relationship can be visualized by considering that if you have two angles, when you place them together, they will complete a straight angle, which is 180 degrees. This concept is fundamental in geometry as it helps understand various configurations and properties of angles in different shapes.

For example, if one angle measures 110 degrees, the other angle must be 70 degrees for them to be supplementary, since 110 + 70 equals 180. Understanding supplementary angles is particularly useful when solving problems related to parallel lines and transversals, where angles formed by these intersections exhibit this supplementary nature.

The other definitions provided do not correctly represent supplementary angles. Two angles that are equal refer to congruent angles, adjacent angles are those that share a common vertex and side but do not need to sum to any specific measure, and angles that form a straight line are specifically the situation of supplementary angles but do not encompass the broader definition that two angles just need to add to 180 degrees without being adjacent or forming a line.