# geometry problem

• December 2nd 2008, 12:39 PM
JoanneMac
geometry problem
I know I'm going to seem like a real stoop, but this has me baffled because there are NO examples like it in my textbook.

Here's the problem: Find the area of a rectangle with length 4 and diagonal 5.

I know to find the area of a rectangle is A=bh, but don't know how to figure in the diagonal part!(Headbang)

Any help is appreciated!!!!
• December 2nd 2008, 12:42 PM
vincisonfire
You must use Pythagore theorem that is $c^2 = a^2 + b^2$ c is the diagonal.
$\sqrt{c^2 - a^2} = b = 3$