In geometry, which angles total 180 degrees?

Supplementary angles are defined as two angles whose measures add up to 180 degrees. This relationship is crucial in various geometric contexts, such as when dealing with straight lines or when calculating angles in polygons.

For example, if one angle measures 120 degrees, the supplementary angle would measure 60 degrees because 120 + 60 equals 180. This property is particularly relevant when two angles are formed on a straight line, which ensures that the angles are supplementary.

In contrast, complementary angles add up to 90 degrees, adjacent angles can share a common vertex and side but do not have a specific angle sum, and vertical angles, formed by the intersection of two lines, are always equal to each other but do not necessarily sum to a specific value like 180 degrees. Therefore, the defining characteristic of supplementary angles makes this choice the correct answer.