Two adjacent angles of a parallelogram have equal measure. Find the measure of each of the angles of the parallelogram.
Let ABCD be the parallelogram with ∠A = ∠B.
We know: Sum of adjacent angles = 180°
∠A + ∠B = 180º
2∠A = 180º (∠A = ∠B)
∠A = 90º
∠B = ∠A = 90º
∠C = ∠A = 90º (Opposite angles)
∠D = ∠B = 90º (Opposite angles)
Thus, each angle of the parallelogram measures 90º.