2. "dihedral angle"-dihedral angle (meaning "two starting points") is one of the four angles formed by the intersection of two non-parallel planes. "complementary angle"-two angles add right angles, that is, they are complementary angles. For example, two acute angles in a right triangle are always considered to be complementary, because their sum is equal to 90 degrees of the right angle. . "Complementary Angle" —— Two angles add up to a flat angle (180) to be complementary angles. If two angles are complementary angles of the same angle, then the two angles are congruent.