Inside the math library are several very common functions. The function named sqrt is the square root function. It takes one parameter--a double--and produces a double. A typical call might look like this:
double d;
d = sqrt(16.0)+3;
In this example, the value 16.0 is passed to the function. It computes the value 4.0, which is then added with 3 and the resulting 7 placed in d