# Math Help - Area Question...

1. ## Area Question...

Prove that the Area of Parallelogram ACC'A' = b^2

2. Originally Posted by MATNTRNG
Prove that the Area of Parallelogram ACC'A' = b^2
If we take it that the triangle with sides a, b, c is right-angled such that $a^2+b^2=c^2$

and the inner shape with sides c is a square, then if we label the angle and side as shown in the attachment..
and the area of the required shape equals the rectangle area,
we only need calculate $kc$.

$Cos\theta=\frac{k}{b}\Rightarrow\ k=bCos\theta$

Using the larger triangle... $Cos\theta=\frac{b}{c}$

Hence, it's straightforward to calculate $kc$ in terms of $b$.