C Programming Code Examples

C > If Else and Switch Case Code Examples

check whether triangle is equilateral, scalene or isosceles

check whether triangle is equilateral, scalene or isosceles

Write a C program to input sides of a triangle and check whether a triangle is equilateral, scalene or isosceles triangle using if else. How to check whether a triangle is equilateral, scalene or isosceles triangle in C programming.

Properties of triangle

    A triangle is said Equilateral Triangle, if all its sides are equal. If a, b, c are three sides of triangle. Then, the triangle is equilateral only if a == b == c.
    A triangle is said Isosceles Triangle, if its two sides are equal. If a, b, c are three sides of triangle. Then, the triangle is isosceles if either a == b or a == c or b == c.
    A triangle is said Scalene Triangle, if none of its sides are equal.

Logic to check equilateral, scalene or isosceles triangle

    Input sides of a triangle from user. Store it in some variables say j1, j2 and j3.
    Check if(j1 == j2 && j2 == j3), then the triangle is equilateral.
    If it is not an equilateral triangle then it may be isosceles. Check if(j1 == j2 || j1 == j3 || j2 == j3), then triangle is isosceles.
    If it is neither equilateral nor isosceles then it scalene triangle.

#include <stdio.h>

int main()
{
    int j1, j2, j3;

    /* Input sides of a triangle */
    printf("Enter three sides of triangle: ");
    scanf("%d%d%d", &j1, &j2, &j3);

    if(j1==j2 && j2==j3) 
    {
        /* If all sides are equal */
        printf("Equilateral triangle.");
    }
    else if(j1==j2 || j1==j3 || j2==j3) 
    {
        /* If any two sides are equal */
        printf("Isosceles triangle.");
    }
    else 
    {
        /* If none sides are equal */
        printf("Scalene triangle.");
    }

    return 0;
}