C语言键盘输入两个实数，求积

键盘输入两个实数，用定义函数的方式，定义一个乘函数求出他们的积。

#include <stdio.h>
double fun(double x, double y);
int main()
{
    double x, y;
    scanf("%lf %lf", &x, &y);
    printf("%lf", fun(x, y));
    return 0;
}

double fun(double x, double y)
{
    return x * y;
}

double fun(double a,double b)
{
return a*b;
}

int main()
{
double a,b;
scanf("%lf%lf",&a,&b);
printf("%lf",fun(a,b));
return 0;
}

#include<stdio.h>
float fun(float x, float y)
{
    return x * y;
}
int main()
{
    float a,b;
    scanf_s("%f %f", &a, &b);
    printf("a*b=%f", fun(a,b));
    return 0;
}