// computes area of a circle, demonstrates function
// Mikhail Nesterenko off of Walter Savitch
// 9/10/2019

#include <iostream>
double circleArea(double r); // computes circle area

using std::cin; using std::cout; using std::endl;

// manage circle computation
int main() {
   cout << "Enter radius: ";
   double radius; // circle radius
   cin >> radius;
   const double area = circleArea(radius);
   cout << "Circle has area " << area << endl;
}

// computes area of radius r circle
double circleArea(double r) {
   const double pi = 3.1415;
   return pi * r * r;
}