In C Pi is defined in math.h - `M_PI`

```
#include <stdio.h>
#include <math.h>
int main ()
{
printf("%lf\n", M_PI);
return(0);
}
```

also you can define Pi in your program

`#define PI 3.141592`

In C Pi is defined in math.h - `M_PI`

```
#include <stdio.h>
#include <math.h>
int main ()
{
printf("%lf\n", M_PI);
return(0);
}
```

also you can define Pi in your program

`#define PI 3.141592`