c program enclosing the variable in the macro expansion

IMPORTANCE OF ENCLOSING THE VARIABLES IN THE MACRO EXPANSION WITHIN PARENTHESIS

#include<math.h>

#define MAC(x,y)sqrt(x*x+y*y)

float fun(int x,int y)

{

    return sqrt(x*x+y*y);

}

void main()

{

    int a=3,b=4;

    float p,q,r,s;

    p=fun(a,b);

    q=fun(a+1,b+1);

    r=MAC(a,b);

    s=MAC(a+1,b+1);

    printf("Using functions:%f,%f\n",p,q);

    printf("Using macros:%f,%f",r,s);

}

OUTPUT

Using functions: 5.0000000,6.403124

Using macros      5.0000000,4.000000