If two alternate interior angles are complementary, what can be said about their measures?

When two alternate interior angles are complementary, their measures sum up to 90 degrees by the definition of complementary angles. Complementary angles are defined as two angles whose measures add up to exactly 90 degrees. In the context of alternate interior angles, which are formed when a transversal crosses two parallel lines, if they are described as complementary, it means that whenever one angle is measured, the other angle will complete the angle sum to 90 degrees.

This scenario does not imply that the angles sum to 180 degrees, which would instead indicate that they are supplementary. The angles being equal is not necessary; they can have different measures as long as their total is 90 degrees. Lastly, one being obtuse is not a requirement either, since one of the angles could be acute while the other is obtuse, or both could be acute while still summing to 90 degrees. Thus, the only consistent relationship determined by their complementary nature is that the two angles will sum to 90 degrees.