How would I set up function to calculate the area of a circle - C

Question

I have this C program that needs to calculate the area of a circle that a user inputs. I have to use this before the main function:

void area_circum(double radius, double *area, double *circum);

I'm having trouble getting the program to work. I'm using the main function and another one called area_circum();

This is what I have right now:

#include <stdio.h>


void area_circum(double radius, double *area, double *circum);

int main(void) {

    double radius, area, circum;

    printf("Please enter the radius of the circle: ");
    scanf("%f", &radius);

    area_circum(radius, area, circum);

    printf("Area of circle : %0.4f\n", area);

    return 0;
}


void area_circum(double radius, double *area, double *circum) {
    double PIE = 3.141;

    double areaC = 0;

    areaC = PIE * radius * radius;
}

When I build it and run it, it works, I input a number, but then it returns 0.00

Answer 1

#include <stdio.h>

void area_circum(double radius);

int main() {

   double radius;

   printf("Please enter the radius of the circle: ");

   scanf("%lf", &radius);

   area_circum(radius);

   return 0;

}


void area_circum(double radius) {

   double PIE = 3.141;

   double areaC = 0;

   areaC = PIE * radius * radius;

   printf("Area of circle : %0.4f\n", areaC);

}