Two angles are complementary, it means that the sum of the angles is 90 degrees
Looking at the diagram,
angle 1 = 90 degrees
Recall, the sum of the angles on a straight line is 180 degrees. This means that
angle 1 + angle 2 + angle 3 = 180
90 + angle 2 + angle 3 = 180
angle 2 + angle 3 = 180 - 9 = 90
Thus, angle 2 and angle 3 are complementary angles
By applying the same idea,
angle 4 and angle 5 are complementary angles
also, angle 8 and 5 are complimentary angles because angle 9 is 90 degrees. This means that angle 8 + angle 5 = 90 degrees