Question

write a program to find the area and the circumference of the circle

Answer 1

we know that the area of the circle having radius R is given by
$\pi {r}^{2} and \: circumference \: is \: given \: by \: 2\pi r \: \\ hence \: we \: may \: write \: circumference of circle as \\ \: 2 \times \frac{area \: of \: cicle}{r}$

Answer 2

#include<stdio.h>

int main() {

  int rad;

  float PI = 3.14, area, ci;

  printf("\nEnter radius of circle: ");

  scanf("%d", &rad);

  area = PI * rad * rad;

  printf("\nArea of circle : %f ", area);

  ci = 2 * PI * rad;

  printf("\nCircumference : %f ", ci);

  return (0);

}