用函数咋做，最好用C语言解答，尽量把过程写出来

#include<stdio.h>
int calc(int num){
if(num==1){
   return 1;
}else{ 
   return num * calc(num-1);
}
}
int main(){
printf("5!/(3!*2!)=%2.0f\n",(calc(5)*1.0/(calc(3)*calc(2))));
return 0;
}