Help please...I'm having a brain fart

[CatDad]

If you still want to know you would modify the Pythagorean theorem.

I can't really make mathimatical symbols here, but it is a sqaured plus b squared = C squared.

So the height is generally referd to as b. That being the case you need to solve for that.

The formula would be:
b = the square root of( a squared minus c squared)

It is really hard to write out if you can't use the proper symbols.

Here is a link to a page that will give you the proper formula:
http://www.webmath.com/cgi/rtri.cgi?c=5&e=&b=%3F&d=&a=4

I hope that helps.