For example, when two lines intersect each other, they the plane into four disjoint domains (http://planetmath.org/Domain2) corresponding to four convex angles; then any of these angles has a supplementary angle on either side of it (see linear pair). However, two angles that are supplementary to each other do not need to have a common side — see e.g. (http://planetmath.org/Eg) an entry regarding opposing angles in a cyclic quadrilateral (http://planetmath.org/OpposingAnglesInACyclicQuadrilateralAreSupplementary).
Supplementary angles have always equal sines, but the cosines are opposite numbers:
These formulae may be proved by using the subtraction formulas of sine and cosine.
|Date of creation||2013-03-22 17:34:59|
|Last modified on||2013-03-22 17:34:59|
|Last modified by||pahio (2872)|