Presuming that , , and have their traditional meanings, that is that and are the legs of the right triangle and is the hypotenuse:
So for your problem
Now just do the arithmetic. Note that 5-12-13 is a Pythagorean Triple and that 10 is 2 times 5 and 24 is 2 times 12. Therefore if you get an answer for that is different from 26, go back and check your arithmetic.