Vertical Angles Small 320×165 Medium 640×330 Large 1024×527 Download Tiff Original 2400×1236 | (299.0 KB) Description Vertical angles are when two angles have the same vertex, and the sides of the one are prolongations of the sides of the other. In this illustration, a and b are vertical angles and c and d are vertical angles. Keywords angle, angles, geometry, line, lines, vertical Galleries Miscellaneous Angles Source: G.A. Wentworth Plane And Solid Geometry (Boston: Ginn & Company, 1899) 13 Courtesy the private collection of Roy Winkelman