Given: m angles A = 90 angles A and angle B are supplementary Prove: angles B is a rt. angle

Answer 1

A+B = 180 (definition of supplementary angles, they sum to 180 degrees)

A =90 substittute 90 for A

90+B =180

B = 180-90 = 90

B =90, therefore B is a right angle (right angles = 90 degrees)