Two angles whose measures add up to 90 degrees are called what?

• A. Vertical Angles
• B. Complementary Angles
• C. Transversal
• D. Corresponding Angles

Answer: (B)

Two angles whose measures add up to 90 degrees are called complementary. This comes from the idea that a right angle measures 90 degrees, so the two angles together fill that right angle. For example, 30 degrees and 60 degrees are complementary. In a right triangle, the two non-right angles are complementary because they sum to 90. The other terms describe different ideas: vertical angles are opposite angles formed by intersecting lines and are equal to each other, not defined by a sum to 90; a transversal is a line that cuts across two lines, and corresponding angles are those in matching positions when a transversal crosses two lines, which are typically equal rather than summing to 90.