If the sum of two angles is 90 degrees, what type of angles are they?

When two angles have a sum of 90 degrees, they are classified as complementary angles. This definition is foundational in geometry: complementary angles add up to 90 degrees. For example, a 30-degree angle and a 60-degree angle are complementary because their sum is exactly 90 degrees.

Understanding angle types will help clarify other options as well. Supplementary angles, for example, add up to 180 degrees, which would not apply in this scenario. Adjacent angles refer to angles that share a common vertex and side but are not necessarily related by their sum. Likewise, vertical angles are formed when two lines intersect; they are equal in measure but are not defined by their sums.

Recognizing the specific definition of complementary angles solidifies why the answer is correct, as it aligns precisely with the given condition of the angles adding up to 90 degrees.