C++ Exercises: Enter two angles of a triangle and find the third angle

Last update on August 11 2025 12:58:13 (UTC/GMT +8 hours)

Third Angle of Triangle

Write a C++ program to enter two angles of a triangle and find the third angle.

Visual Presentation:

C++ Exercises: Enter two angles of a triangle and find the third angle

Sample Solution:

C++ Code :

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

using namespace std; // Using the standard namespace

int main() // Start of the main function
{
    float ang1, ang2, ang3; // Declaring variables to store angles of a triangle

    cout << "\n\n Find the third angle of a triangle :\n"; // Displaying the purpose of the program
    cout << "-----------------------------------------\n";

    cout << " Input the 1st angle of the triangle : "; // Prompting the user to input the 1st angle of the triangle
    cin >> ang1; // Taking input of 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 of the 2nd angle from the user

    ang3 = 180 - (ang1 + ang2); // Calculating the 3rd angle of the triangle using the sum of angles
    cout << " The 3rd angle of the triangle is : " << ang3 << endl; // Displaying the calculated 3rd angle

    cout << endl; // Displaying an empty line for better readability

    return 0; // Returning 0 to indicate successful program execution
}

Sample Output:

Find the third angle of a triangle :                                  
-----------------------------------------                              
 Input the 1st angle of the triangle : 35                              
 Input the 2nd angle of the triangle : 35                              
 The 3rd of the triangle is : 110

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to calculate the third angle of a triangle and validate the input so that the sum of the two angles is less than 180°.
Write a C++ program that computes the third angle, then categorizes the triangle as acute, right, or obtuse based on all three angles.
Write a C++ program to calculate the missing angle of a triangle using user-defined functions and incorporate error handling for invalid angles.
Write a C++ program that reads two angles and calculates the third angle, then prints a warning if the triangle is nearly degenerate.

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