c primer plus 第十六章课后编程2题

//用宏函数定义俩个数的调和平均数
#include <stdio.h>
#define HARMONIC_MEAN(X,Y) 2/((1/X)+(1/Y))

int main(void)
{
double x=5.0;
double y=13.0;
printf(“x and y Harmonic mean: %lf\n”,HARMONIC_MEAN(x,y));

return 0;

}