#include <cmath>
    double sqrt( double num );

The sqrt() function returns the square root of num. If num is negative, a domain error occurs.

C++ also provides the following overloaded forms:

    #include <cmath>
    float sqrt( float num ); // same as sqrtf() in C99
    long double sqrt( long double num ); // same as sqrtl() in C99

Related Topics: exp, log, pow