lucproblem004.c

Problem Statement

lucproblem004.c

If the lengths of three sides of a triangle are entered through the keyboard, write a program to check whether the triangle is valid or not. The triangle is valid if the sum of two sides is greater that the largest of the three sides.

Source Code

#include <stdio.h>
int main()
{
    double side1, side2, side3;
    printf("Enter the length of side1, side2 and side3 of the triangle : ");
    scanf("%lf %lf %lf", &side1, &side2, &side3);
    if (side1 <= 0 || side2 <= 0 || side3 <= 0)
    {
        printf("\nTriangle sides must be positive.\n");
        return 1;
    }
    if ((side1 + side2 > side3) && (side1 + side3 > side2) && (side2 + side3 > side1))
    // Triangle Inequality Theorem
        printf("\nThis triangle is valid.");
    else
        printf("\nThis triangle is not valid.");
    return 0;
}

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● Author - Amit Dutta · Updated - 12 Dec 2025