Construction to Find the Third Angle of a Triangle When Given Two Angles Small 320×175 Medium 640×349 Large 1024×559 Download Tiff Original 2400×1309 | (132.2 KB) Description Illustration of the construction used to find the third angle of a triangle when two of the angles are given. Keywords angles, construction, constructions, given two angles of a triangle, third angle of triangle, triangles Galleries Geometric Constructions Source: G.A. Wentworth Plane And Solid Geometry (Boston: Ginn & Company, 1899) 118 Courtesy the private collection of Roy Winkelman