The library, courthouse, and pool form a right triangle (with the courthouse as the right angle). You can use the Pythagorean theorem to find the distance between the library and the pool. The theorem states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.
So, the distance between the library and the pool is the square root of (6^2 + 10^2), which is approximately 11.66 miles.