# Have to use pythagoras theorem

In parallelogram ABCD, the diagonals AC is at right angles to AB.If AB=12 & AC=13. I have to find the area of parallelogram. How can I use Pythagoras theorem here? I do not understand.

• Are you sure you're supposed to use the Pythagorean theorem? It's not what I'd use for this problem. – Jack M Feb 18 '15 at 14:35
• Have you drawn the parallelogram? – Gobabis Feb 18 '15 at 14:36
• yes i have drawn but confused about it.i have to use pythagorean theorem because it is taken from pythagoras theorem exercise – tanz Feb 18 '15 at 14:41
• I can see no reason to work out the length of BC as you have AB as the base and AC as the hieght – Gobabis Feb 18 '15 at 14:47
• Your question doesn't make sense. Take a look at: algebra.com/algebra/homework/Pythagorean-theorem/… – user137035 Feb 18 '15 at 15:07

The area of a parallogram is the product of base and height. In your case, the base is AB and the height is AC, so the area is just $12\cdot13=156$, so no need of Pythagoras' theorem. You can use it, however, to calculate $BC=\sqrt{AB^2+AC^2}$.