Question

Using the idea of inheritance and polymorphism write a C++ program that calculates the area of regular polygons.

This is a typical output when the desired program is executed:

>> please enter the sides of your polygon: 3,4,5

>> Your polygon is a triangle and its area is: 6

In your program, you must check that the values entered are correct and can build a polygon. The number of the digits entered initially can help software to determine the polygon type. For example, if 4 numbers are entered then it is a 4 sided polygon.

Answer 1

#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
//abstract base class
class base
{
protected :
double a,b,c,ar;
public:
virtual void input()=0;
virtual void area()=0;
};
//triangle derived class
class triangle : public base
{
public:
void input();
void area();
};
//quadrilateral derived class
class quadrilateral : public base
{
public:
void input();
void area();  
};
//pentagon derived class
class pentagon : public base
{
public:
void input();
void area();  
};
//hexagon derived
class hexagon : public base
{
public:
void input();
void area();  
};
//heptagon derived class
class heptagon : public base
{
public:
void input();
void area();  
};
//octagon derived class
class octagon : public base
{
public:
void input();
void area();  
};
//nonagon derived class
class nonagon : public base
{
public:
void input();
void area();  
};
//decagon derived class
class decagon : public base
{
public:
void input();
void area();  
};
//input method for triangle
void triangle :: input()
{
    cout<<endl<<"Enter the three sides of triangle";
    cin>>a>>b>>c;
}
//input method for quadrilateral
void quadrilateral :: input()
{
    cout<<endl<<"Enter the side of quadrilateral";
    cin>>a;
}
//input method for pentagon
void pentagon :: input()
{
    cout<<endl<<"Enter the side of pentagon";
    cin>>a;
}
//input method for hexagon
void hexagon :: input()
{
    cout<<endl<<"Enter the side of hexagon";
    cin>>a;
}
//input method for heptagon
void heptagon :: input()
{
    cout<<endl<<"Enter the side of heptagon";
    cin>>a;
}
//input method for octagon
void octagon :: input()
{
    cout<<endl<<"Enter the side of octagon";
    cin>>a;
}
//input method for nonagon
void nonagon :: input()
{
    cout<<endl<<"Enter the side of nonagon";
    cin>>a;
}
//input method for decagon
void decagon :: input()
{
    cout<<endl<<"Enter the side of decagon";
    cin>>a;
}
//area for triangle
void triangle :: area()
{
   double s;
   s=(a+b+c)/2;
   s= s * (s-a) * (s-b) * (s-c);
   s=sqrt(s);
   cout<<endl<<"Your Polygon is a triangle and its area is : "<<s<<" sq. units.";
}
//area for quadrilateral
void quadrilateral :: area()
{
    cout<<endl<<"Your Polygon is a quadrilateral and its area is : "<<a*a<<" sq. units.";
}

//area for pentagon
void pentagon :: area()
{
   double t;
   t= sqrt(5);
   t= 2*t;
   t= 5+t;
   t=5*t;
   t=sqrt(t);
   t= 0.25 * t * (a*a);
   cout<<endl<<"Your Polygon is a pentagon and its area is : "<<t<<" sq. units.";  
   }
   //area of hexagon
   void hexagon :: area()
{
   double t;
   t=sqrt(3);
   t=3*t;
   t=t/2;
   t=t * (a*a);
   cout<<endl<<"Your Polygon is a hexagon and its area is : "<<t<<" sq. units.";  
   }
//area of heptagon
   void heptagon :: area()
{
   double t;
   t=1.75 * a*a;
   t= t * cos(25.71)/sin(25.71);
   cout<<endl<<"Your Polygon is a heptagon and its area is : "<<t<<" sq. units.";  
   }
  
   //area of octagon
   void octagon :: area()
{
   double t;
   t=sqrt(2);
   t=2*(1+t)*(a*a);
   cout<<endl<<"Your Polygon is a heptagon and its area is : "<<t<<" sq. units.";  
   }
   //area of octagon
   void nonagon :: area()
{
   double t;
   t=2.25 * (a*a);
   t= t * cos(20)/sin(20);
   cout<<endl<<"Your Polygon is a nonagon and its area is : "<<t<<" sq. units.";  
   }
   //area of octagon
   void decagon :: area()
{
   double t;
   t=sqrt(5);
   t=2*t;
   t=5+t;
   t=sqrt(t);
   t= 2.5 *(a*a) *t;
   cout<<endl<<"Your Polygon is a decagon and its area is : "<<t<<" sq. units.";  
   }
int main()
{
   int n,opt=1;
base *obj;
//derived class objects
triangle t;
quadrilateral q;
pentagon p;
hexagon h;
heptagon he;
octagon oc;
nonagon no;
decagon de;
//infinite loop
while(opt==1)
{
    cout<<"Enter the number of sides of polygon";
    cin>>n;
    //check the validity of sides
    if(n<3 || n>10)
    {
    cout<<endl<<"Invalid Polygon";
   break;   
   }
   //block for triangle
    if(n==3)
    {
       obj=&t;
           obj->input( );
           obj->area();
       }
       else
       if(n==4) //block for quadrilateral
    {
       obj=&q;
           obj->input( );
           obj->area();
       }
       else
       if(n==5) //block for pentagon
    {
       obj=&p;
           obj->input( );
           obj->area();
       }
       else
       if(n==6) //block forhexagon
    {
       obj=&h;
           obj->input( );
           obj->area();
       }
       else
       if(n==7) //block for heptagon
    {
       obj=&he;
           obj->input( );
           obj->area();
       }
    else
    if(n==8) //block for octagon
    {
       obj=&oc;
           obj->input( );
           obj->area();
       }
       else
       if(n==9) //block for nonagon
    {
       obj=&no;
           obj->input( );
           obj->area();
       }
       else
       if(n==10) //block for decagon
    {
       obj=&de;
           obj->input( );
           obj->area();
       }
       cout<<endl<<"Do you want to compute more, Enter 1 to continue, any value to stop";
       cin>>opt;
         
}

}

OUTPUT

NOTE: FOR SIDE 4 I HAVE COMPUTED FOR SQUARE, IF YOU NEED FOR ALL QUADRILITERALS THEN INFORM.