Documentation for sqrt function

The prewritten function illustrated by Listing 1 is named sqrt.

Figure 1 shows the documentation for the sqrt function as obtained from this web site:

double  sqrt ( double x );

Calculate square root.
  Returns the square root of parameter x.

Parameters.

x
Non-negative floating point value.

Return Value.
  Square root of x.

Portability.
  Defined in ANSI-C.
  ANSI-C++ adds float and double overloaded versions of this function, with the same behavior but being both, parameter and result, of one of these types. 

Figure 1

According to the documentation, the sqrt function requires a single incoming parameter of type double.

It returns the square root of the incoming value as type double.