A complementary angle is a pair of 2 angles that when added together, would be 90 degrees. A supplementary angle is a pair of 2 angles that when added together, would be 180 degrees. How a complementary angle can be classified is if the 2 angles are acute angles since 2 acute angles combined together make a right angle and a right angle is 90 degrees. A supplementary angle can be classified by 2 right angles combined together which make a straight line that is 180 degrees since a right angle is 90 degrees so 2 right angles 90+90=180 which make a straight line hope this helps