Use the Pythagorean theorem; substitute the measurement of the leg into either a or b, and substitute the value of the hypotenuse into c.
The Pythagorean theorem states that the sum of the squares of the two legs of a right triangle is equal to the square of the hypotenuse; algebraically,
a²+b² = c².
To find the measure of the unknown leg, we substitute the information we know; the known leg will be either a or b (it does not matter which), and the hypotenuse will be c.
since the pythagorean theorem is a^2+b^2=c^2, you have to plug in the lengths of the leg and the hypotenuse to the formula. If you were trying to find a, you would plug in the second leg into b and the hypotenuse into c. so if for example you needed to find a and the second leg was 2 inches while the hypotenuse was 5 inches, the formula would be a^2+2^2=5^2. then solve it like a regular equation, so a^2+4+25, a^2=21, and you would do the square root of that answer. hope that helped.
