C Exercises: Check whether a triangle can be formed by given value

Last update on July 29 2025 12:51:44 (UTC/GMT +8 hours)

15. Triangle Validity by Angles

Write a C program to check whether a triangle can be formed with the given values for the angles.

Visual Presentation:

Sample Solution:

C Code:

#include <stdio.h>  // Include the standard input/output header file.

void main()  
{  
    int anga, angb, angc, sum; // Declare variables for the angles of the triangle.

    printf("Input three angles of triangle : ");  // Prompt user for input.  
    scanf("%d %d %d", &anga, &angb, &angc);  // Read and store the angles of the triangle.

    /* Calculate the sum of all angles of triangle */  
    sum = anga + angb + angc;   

    /* Check whether sum=180 then its a valid triangle otherwise not */  
    if(sum == 180)   
    {  
        printf("The triangle is valid.\n");  // Print message for valid triangle.
    }  
    else  
    {  
        printf("The triangle is not valid.\n");  // Print message for invalid triangle.
    }  
 } 

Output:

Input three angles of triangle : 40 55 65                                                                     
The triangle is not valid.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to check if three given angles can form a triangle and output an error if they do not.
• Write a C program to validate triangle angles using only arithmetic operations without conditional statements.
• Write a C program to check triangle validity with angles and compute the area using trigonometric formulas if valid.
• Write a C program to accept three angles, verify triangle validity, and then output the triangle’s classification based on its angles.

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