Create an application program that will compute theradius and circumference of a circle. write a main class methods to prompt for and input the radius of acircle(getradius), calculate thecircumference(calccirc), and calculate thearea(calcarea) of a circle. define the radius, area, and circumference in main which will call each calc method, passing radius to each one. assume pi = 3.14159 or use themath. pi builtin constant. format theoutput to show two decimal places in the calculatedvalues.

The c++ program is given below.

#include <iostream>

#include<iomanip>

using namespace std;

double getRadius();

double calcCirc(double r);

double calcArea(double r);

int main() {

   double radius, area, circumference;

   int r, c, a;    

   radius = getRadius();

   if(radius>0 && radius<10)

       r=3;

   if(radius>10 && radius<100)

       r=4;

   if(radius>100 && radius<1000)

       r=5;

   cout<<"The radius of the circle is "<<setprecision(r)<<radius<<endl;

   circumference=calcCirc(radius);

   if(circumference>0 && circumference<10)

       c=3;

   if(circumference>10 && circumference<100)

       c=4;

   if(circumference>100 && circumference<1000)

       c=5;

   cout<<"The circumference of the circle is "<<setprecision(c)<<circumference<<endl;

   area=calcArea(radius);

   if(area>0 && area<10)

       a=3;

   if(area>10 && area<100)

       a=4;

   if(area>100 && area<1000)

       a=5;

   cout<<"The area of the circle is "<<setprecision(a)<<area<<endl;

}

double getRadius()

{

   double r;

   cout<<"Enter the radius of the circle : "<<endl;

   cin>>r;

   return r;

}

double calcCirc(double r)

{

   double PI = 3.14159;

   return (2*PI*r);

}

double calcArea(double r)

{

   double PI = 3.14159;

   return (PI*r*r);

}

OUTPUT

Enter the radius of the circle :

11.1111

The radius of the circle is 11.11

The circumference of the circle is 69.81

The area of the circle is 387.85

Explanation:

As per the requirement, all the variables radius, area, and circumference are declared with data type double in main function.

The methods getRadius, calcCirc, calcArea are declared with return type double.

getRadius

This method prompts the user to input the radius and returns the radius to the calling function main. This value is stored in variable radius.

calcCirc

This method takes radius as input, calculates the circumference and returns the circumference to the calling function main. This value is stored in variable circumference.    

calcArea

This method takes radius as input, calculates the area and returns the area to the calling function main. This value is stored in variable area.

All the three values are displayed with two decimal places. This is achieved using setprecision() method.

The number of digits is inclusive of 2 decimal places and all digits before the decimal. This value is declared based on the values of radius, circumference and area. The total number of digits is passed as a parameter to the setprecision() method.

All the values are displayed with two decimal places.