An angle measures 54 degrees. In order to correctly determine the measure of its complementary angle, what concept is necessary?

To find the measure of a complementary angle, it is essential to understand that complementary angles are defined as two angles that sum up to 90 degrees. Given an angle measuring 54 degrees, its complementary angle can be calculated by subtracting this angle from 90 degrees.

Thus, the calculation would be:

90 degrees - 54 degrees = 36 degrees.

The resulting value, 36 degrees, denotes the measure of the angle that, when added to the original 54 degrees, totals 90 degrees.

Understanding this fundamental concept about the relationship between complementary angles allows for correct applications in problems involving angle measures in geometry.