Area of Triangle

| View Cart ⇗ | Info

“The child sees triangle ACB = triangle ADB, and that I + II = CA - DB; and so he sees that the area of triangle=1/2 area of rectangle whose base and altitude are the same as those of the triangles.” -Foster, 1921


Ellsworth D. Foster ed. The American Educator (vol. 1) (Chicago, IL: Ralph Durham Company, 1921)


TIFF (full resolution)

2400×2059, 177.0 KiB

Large GIF

1024×878, 23.0 KiB

Medium GIF

640×549, 13.9 KiB

Small GIF

320×274, 6.2 KiB