I have to write a function to find the circumference of a circle. I am having problems cause I dont have any idea how to do that. I know ya'll like to have some kind of showing of my own program the only thing is that I dont understand what to do or where to start. My teacher is no help. I dont like the way he teaches. Maybe someone here can get me to understand a function with an example or something.

My program started

```
#include<iostream.h>
void my_sum(int r)
{
float sum;
sum = 2*3.14*r;
cout<<"The circumference of a circle is "<<sum<<"."<<endl;
}
int main()
{
```

Im stuck. I dont think this is even right. I dont know what I am doing. Please someone help.

Kelly