C Exercises: Check whether a triangle is Equilateral, Isosceles or Scalene

C Conditional Statement: Exercise-14 with Solution

Write a C program to check whether a triangle is Equilateral, Isosceles or Scalene.

Equilateral triangle: An equilateral triangle is a triangle in which all three sides are equal. In the familiar Euclidean geometry, equilateral triangles are also equiangular; that is, all three internal angles are also congruent to each other and are each 60°.

Isosceles triangle: An isosceles triangle is a triangle that has two sides of equal length.

Scalene triangle: A scalene triangle is a triangle that has three unequal sides, such as those illustrated above.

Pictorial Presentation:

Sample Solution:

C Code:

#include <stdio.h>
int main()  
{  
    int sidea, sideb, sidec; //are three sides of a triangle  
  
    /* 
     * Reads all sides of a triangle 
     */  
    printf("Input three sides of triangle: ");  
    scanf("%d %d %d", &sidea, &sideb, &sidec);  
  
    if(sidea==sideb && sideb==sidec) //check whether all sides are equal  
    {  
        printf("This is an equilateral triangle.\n");  
    }  
    else if(sidea==sideb || sidea==sidec || sideb==sidec) //check whether two sides are equal  
    {  
        printf("This is an isosceles triangle.\n");  
    }  
    else //check whether no sides are equal  
    {  
        printf("This is a scalene triangle.\n");  
    }  
  
    return 0;  
} 

Sample Output:

Input three sides of triangle: 50 50 60                                                                       
This is an isosceles triangle.

Flowchart:

C Programming Code Editor:

Improve this sample solution and post your code through Disqus.

Previous: Write a C program to read temperature in centigrade and display a suitable message according to temperature state below.
Next: Write a C program to check whether a triangle can be formed by the given value for the angles.