# Write a Program to calculate area of a circle, a rectangle or a triangle depending upon user's choice

Posted in  Vinay Khatri
Last updated on November 14, 2022

## Problem Statement

We need to write a program in C, C++, and Python, that is capable of returning the area of a circle, rectangle, and triangle based on the user's choice and input.

First, the user has the choice to select the geometry for which he/she wants to calculate the area. Then based on the geometry shape selected asks the user for the sides or radius of the shape and calculate its area.

To calculate the areas of Circle, Rectangle, and Triangle we will use the following formulas. area of circle = ``` ? r 2 ``` area of the rectangle = ``` width*length ``` area of a triangle(with three sides given a, and c) = ``` ?[s(s-a)(s-b)(s-c)] ``` , where s = (a+b+c)/2

### C Program to calculate the area of a circle, a rectangle, or a triangle depending upon the user's Choice

``````#include <stdio.h>
#include <math.h>

int main()
{
float area, radius, width, length, a, b, c,s;
int choice;

printf("**********Choose an Option:*********\n ");
printf("1: Area of the Circle\n ");
printf("2: Area of the Rectangle\n ");
printf("3: Area of the Triangle\n ");

//input the geometry shape
scanf("%d", &choice);

//for circle
if(choice==1)
{
printf("Enter the radius of the Circle: ");
printf("The area of the circle with radius %f is %.2f", radius, area);
}

//for rectangle

if(choice ==2)
{
printf("Enter the Width of the rectangle: ");
scanf("%f", &width);
printf("Enter the length of the rectangle: ");
scanf("%f", &length);

area = width*length;
printf("The area of the rectangle is %.2f", area);
}
//area of triangle using heron's formula
if(choice ==3)
{
printf("Enter the 3 sides of triangle eg (12 13 14):  ");
scanf("%f %f %f", &a, &b, &c);
s = (a+b+c)/2;
area = sqrt(s*(s-a)*(s-b)*(s-c));
printf("The area of the triangle is %.2f", area);
}
return 0;
}``````

Output

``````**********Choose an Option:*********
1: Area of the Circle
2: Area of the Rectangle
3: Area of the Triangle
3
Enter the 3 sides of triangle eg (12 13 14): 3 7 6
The area of the triangle is 8.94``````

### C++ Program to calculate the area of a circle, a rectangle, or a triangle depending upon the user's Choice

``````#include
#include
using namespace std;

int main()
{
float area, radius, width, length, a, b, c,s;
int choice;

cout<<"**********Choose an Option:*********\n ";
cout<<"1: Area of the Circle\n ";
cout<<"2: Area of the Rectangle\n ";
cout<<"3: Area of the Triangle\n ";

//input the geometry shape
cin>>choice;

//for circle
if(choice==1)
{
cout<<"Enter the radius of the Circle: ";
cout<<"The area of the circle with radius "<< radius<<" is "<< area;
}

//for rectangle

if(choice ==2)
{
cout<<"Enter the Width of the rectangle: ";
cin>>width;
cout<<"Enter the length of the rectangle: ";
cin>>length;

area = width*length;
cout<<"The area of the rectangle is "<< area;
}
//area of triangle using heron's formula
if(choice ==3)
{
cout<<"Enter the 3 sides of triangle eg (12 13 14): ";
cin>>a>>b>>c;
s = (a+b+c)/2;
area = sqrt(s*(s-a)*(s-b)*(s-c));
cout<<"The area of the triangle is "<< area;
}
return 0;
}``````

Output

``````**********Choose an Option:*********
1: Area of the Circle
2: Area of the Rectangle
3: Area of the Triangle
2
Enter the Width of the rectangle: 12
Enter the length of the rectangle: 6
The area of the rectangle is 72``````

### Python Program to calculate the area of a circle, a rectangle, or a triangle depending upon the user's Choice

``````import math

print("**********Choose an Option:********* ");
print("1: Area of the Circle");
print("2: Area of the Rectangle ");
print("3: Area of the Triangle ");

# input the geometry shape
choice = int(input(""))

# area of the circle
if choice==1:

#area of the rectangle
if choice==2:
width =float(input("Enter the width of the rectangle: "))
length = float(input("Enter the length of the rectangle: "))
area = width*length
print(f"The area of the ractangle is {round(area,2)}")

# area of triangle using heron's formula
if choice ==3:
a, b , c = map(float, input("Enter the 3 sides of triangle eg (12 13 14):").split())
s= (a+b+c)/2
area = math.sqrt(s*(s-a)*(s-b)*(s-c))
print(f"The area of the triangle is {round(area,2)}")``````

Output

``````**********Choose an Option:*********
1: Area of the Circle
2: Area of the Rectangle
3: Area of the Triangle
1
Enter the radius of the Circle: 12
The area of the circle with radius 12.0 is : 452.39``````

## Wrapping UP!

In this programming tutorial, we discussed how to write a program in C, C++, and Python to find out the area of a Circle, Rectangle or Triangle. The program is quite simple and works on the user's choice. To calculate the circle area it asks the user to enter the radius of the circle. For the rectangle, it asks for width and length. And for the triangle, it accepts the lengths of three sides.