#include <math.h>float hypotf(float side1, float side2);double hypot(double side1, double side2); long double hypotl(long double side1, long double side2);
hypot( ), hypotf( ), and hypotl( ) functions were added by C99.
The hypot( ) family of functions returns the length of the hypotenuse given the lengths of the two opposing sides. That is, it returns the square root of the sum of the squares of side1 and side2.
A related function is sqrt( ).