C++ Exercises: Find the third angle of a triangle

Last update on August 11 2025 12:57:26 (UTC/GMT +8 hours)

Find Third Angle of Triangle

Write a C++ program to find the third angle of a triangle.

Visual Presentation:

C++ Exercises: Find the third angle of a triangle

Sample Solution:

C++ Code :

#include <iostream> // Including the input-output stream header file

using namespace std; // Using the standard namespace

int main() // Start of the main function
{
    float ang1, ang2, ang3; // Declaring floating-point variables for angles of the triangle

    cout << "\n\n Find the third angle of a triangle :\n"; // Outputting a message indicating calculation of the third angle
    cout << "-----------------------------------------\n"; // Outputting a separator line

    cout << " Input the 1st angle of the triangle : "; // Prompting the user to input the 1st angle of the triangle
    cin >> ang1; // Taking input for the 1st angle from the user

    cout << " Input the 2nd angle of the triangle : "; // Prompting the user to input the 2nd angle of the triangle
    cin >> ang2; // Taking input for the 2nd angle from the user

    ang3 = 180 - (ang1 + ang2); // Calculating the third angle of the triangle: 180 - (sum of the 1st and 2nd angles)

    cout << " The 3rd of the triangle is : " << ang3 << endl; // Displaying the calculated third angle of the triangle
    cout << endl; // Outputting a blank line for better readability

    return 0; // Returning 0 to indicate successful program execution
} // End of the main function

Sample Output:

 Find the third angle of a triangle :                                  
-----------------------------------------                              
 Input the 1st angle of the triangle : 30                              
 Input the 2nd angle of the triangle : 60                              
 The 3rd of the triangle is : 90

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to compute the third angle of a triangle after validating that the sum of the first two angles is less than 180°.
Write a C++ program that calculates the missing angle of a triangle and prints an error if the input angles are invalid.
Write a C++ program to determine the third angle of a triangle using user-defined functions and proper input validation.
Write a C++ program that reads two angles, computes the third angle, and then categorizes the triangle based on its angles.

Go to:

PREV : Fahrenheit to Celsius Conversion.
NEXT : Kilometers to Miles Conversion.

C++ Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.