Calculating the Length of Triangle Sides
In a right triangle the side opposite the right angle (c below) is equal to the square root of the sum of the squares of the other two sides.
In a right triangle either of the sides forming the right angle may be found by subtracting the square of the other side from the square of the side opposite the right angle and taking the square root.
When estimating roof framing these calculations can also assist in determining rafter lengths.