We are asked to find the length of the board used for a brace. We will call this length l. Let's draw a diagram describing this situation.
If we assume that the board is rectangular, then a brace divides the board into two right triangles. Therefore, we can use the Pythagorean Theorem to evaluate l. Recall that, according to this theorem, the sum of the squared legs of a right triangle is equal to its squared hypotenuse.
3^2+ 8^2= l^2
Let's solve the equation. Notice that since l represents the length, we will consider only the positive case when taking a square root of l^2.
