Complementary angles: angles whose sum is 90 degrees.supplementary angles: angles whose sum is 180 degrees.straight angle: an angle that is worth 180 degrees. (can be a straight line)right angle: an angle that is worth 90 degrees ( usually marked by a small box and is the angle in a rectangle and square)
Which statement is not always true for a parallelogram? (a) opposite sides are congruent. (b) diagonals bisect each other. (c) it has 4 congruent angles. (d) consecutive angles are supplementary.