Area of a Triangle  2.

The formula for the area of a triangle is A = (1/2)bh  where b is the base and h is the height.
If you already know the formula for the area of a triangle,  it is easy to recognize that it is half the area of a parallelogram with the same base and height, which suggests another derivation of the formula. 

This page will be no fun if you don't get the images.

Note that this justification holds for any shape triangle, with any side treated as the base.

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 Rectangle :  Parallelogram :  Triangle 1. :  Triangle 2.  :  Trapezoid 1.  :  Trapezoid 2. :  Circle 1. :  Circle 2.

Animations by Bettina Richmond and Tom Richmond.
Updated May 22, 2008.