# Area of Triangle

## 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

## Galleries

## Source:

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

Courtesy the private collection of Roy Winkelman