square of difference of sqrt

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
double reverse(const double a, const double b) {
  double ret = sqrt(a) - sqrt(b);
  return ret * ret;
}
int main(void) {
  printf("%lf\n", reverse(1., 2.));
  printf("%lf\n", reverse(2., 3.));
  printf("%lf\n", reverse(3., 4.));
  return 0;
}