COMPLEMENT (Lat. complementum, from compleo, to fill up), the full number or quantity requisite to completeness: that which is wanted to complete some quantity or thing. Thus the complement of an angle is the difference between the given angle and a quadrant, or 90°. To find the complement of any given angle expressed in degrees, minutes, and seconds, subtract it from 90° if acute; or if obtuse, subtract 90° from it. The complements of a paral-
lelogram are the two spaces which, together with the parallelograms about the diagonal, make up the whole figure.