Two angles are called complementary if their measures add to 90 degrees, and called supplementary if their measures add to 180 degrees. If two angles are complementary then they will add up to be 90, or inversely, if two angles add up to be 90, then they are complementary. If you know one acute angle, you can calculate its complementary angle by subtracting 90 and the angle. When the sum of two angles is equal to 90 degrees, they are called complementary angles. For example, 30 degrees and 60 degrees are complementary angles.
The complement of −135° is the angle that when added to −135° forms a right angle (90° ).
