area and circumference of a circle

1C = Pi * r * 2 (r stands for radius)
2
3Or you could do this:
4C = Pi * d (d stands for diameter)

1curcomfrance = pi * radius * 2

1#include <stdio.h>
2#define PI 3.142
3int main(){
4    float r, C, A;
5    printf("What is the radius: \n");
6    scanf("%f", &r);
7    C = 2 * PI * r;
8    A = PI * r * r;
9    printf("\nCincumference is and %f Area is %f\n", C, A);
10}

1from math import pi
2Circumference = pi * diameter  
3Circumference = pi * 2 * radius