Illustration of supplementary angles. Two angles whose sum is a straight angle. This can be used tow show the Theorem: If two adjacent angles are supplementary, their exterior sides are in the same straight line.
Keywordsgeometry, angle, angles, sum, supplementary, 180 degrees, straight line, supplement, supplements
G.A. Wentworth Plane And Solid Geometry (Boston: Ginn & Company, 1899) 17