Isosceles Triangle With Parallelogram inside Small 276×320 Medium 553×640 Large 884×1024 Download Tiff Original 2073×2400 | (229.3 KB) Description Illustration to show that if from any point in the base of an isosceles triangle parallels to the legs are drawn, a parallelogram is formed whose perimeter is constant, being equal to the sum of the legs of the triangle. Keywords inside triangles, interior, isosceles, leg, Legs, parallelogram, perimeter, triangle Galleries Miscellaneous Triangles Source: G.A. Wentworth Plane And Solid Geometry (Boston: Ginn & Company, 1899) 71 Courtesy the private collection of Roy Winkelman