When you know the two legs of a right angled triangle, but don’t know the hypotenuse, you can always use the Pythagorean Theorem. Square each leg, and add them together. You will find the answer is the hypotenuse squared. To find the final answer find the square root.  If you know the hypotenuse and one of the legs, but not the other one, you can use the Pythagorean Theorem backward. Square the numbers you know. Subtract one of the legs from the hypotenuse, you will end up with the answer for one of the legs squared. You need to find the square root and you end up with the final answers.