What is the relationship between complementary angles?

The relationship between complementary angles is that they sum to 90 degrees. This means that when you take two angles that are complementary, if you add their measures together, the total will always equal 90 degrees. This concept is fundamental in geometry and is often used in various mathematical applications, such as solving problems involving angles in triangles or calculating the measures of unknown angles.

The other options highlight different relationships between angles. For instance, while equal angles refer to angles that have the same measure, complementary angles do not need to be equal. The option stating that complementary angles add up to 180 degrees describes supplementary angles instead, which is a different concept. Lastly, while adjacent angles can be complementary, this is not a requirement for all complementary angles, as they do not have to share a common vertex or side. Thus, the definition of complementary angles specifically pertains to their sum being 90 degrees.