The Program in C to calculate the area of a circle is given below:

```
#include <stdio.h>
#define PI 3.14159 // define constant PI
int main() {
double radius, area;
printf("Enter the radius of the circle: ");
scanf("%lf", &radius);
area = PI * radius * radius; // formula to calculate area of circle
printf("The area of the circle with radius %lf is %lf", radius, area);
return 0;
}
```

## Output:

Enter the radius of the circle: 87

The area of the circle with radius 87.000000 is 23778.694710

Note that this program uses the constant PI and the area of a circle is calculated using the formula A = PI * r^2.

Also, you can include library and use M_PI instead of 3.14159 for more precise value of pi.

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