Write inline functions of circular area of

Write inline function CalArea (double radius) to find the area of ​​the circle (where: Pi = 3.14).

#include <iostream>
#define pi 3.14
using namespace std;
double CalArea(double &r)
{
 return pi*r*r;
}
int main()
{
    double radius, area;
    cin >> radius;
    double r(radius);
    area = CalArea(r);
    cout << area << endl;
}