Area of Triangle Small 320×140 Medium 640×279 Large 1024×447 Download TIFF Original 2400×1047 | (129.6 KB) Description "Fig. 3 shows triangle I = triangle II, III = IV, and so triangle ABC = 1/2 of rectangle ABDE. The fact is realized that the area of a triangle equals 1/2 the product of the base and altitude." -Foster, 1921 Keywords equal triangles, half base times height, rectangle, right triangles, triangle area Galleries Miscellaneous Triangles Source: Ellsworth D. Foster ed. The American Educator (vol. 1) (Chicago, IL: Ralph Durham Company, 1921)