Noun
supplementary angles
(geometry) plural of supplementary angle
Let angle A = 30° and angle B = 10°, so that their supplementary angles are A′ = 150° and B′ = 170°, respectively.
supplementary angles pl (plural only)
(geometry) A pair of angles that sum to 180 degrees.
A = 30° and A′ = 150°, so A and A′ are supplementary angles.