Question

Input the radius of a circle, and output the area. (The formula for area is PI times r squared, where PI is 3.141592653589793 and r is the radius.)

Answer 1

Here I wrote the code in C programming language. Please comment for further assistance.

#include <stdio.h>

int main()

{
double pi = 3.141592653589793;
double r;
scanf("%lf",&r);
printf("Area: %lf",pi*r*r);

return 0;
}