Determine Triangle Type in C++

This C++ exercise focuses on conditional logic and input handling. The program asks the user to input the lengths of the three sides of a triangle and determines whether it is equilateral, isosceles, or scalene.

This activity enhances your understanding of nested conditionals, logical operators (&&, ||), and basic geometry principles applied in programming.

Triangle Definitions

Equilateral

All three sides are equal in length. (a == b && b == c)

Isosceles

At least two sides are equal in length. (a == b || a == c...)

Scalene

All three sides have different lengths. (a != b && b != c...)

The Triangle Inequality Theorem

Before classifying, the program must verify if a triangle is even possible. The sum of any two sides must be greater than the third side (e.g., a + b > c).

Objectives

1. Input three side lengths using float or double.
2. Implement the Triangle Inequality Theorem to validate the input.
3. Use nested if-else structures to categorize the triangle.
4. Output the specific type or an error message if the triangle is invalid.

Example C++ Code

triangle_type.cpp Logic & Geometry

#include <iostream>

using namespace std;

int main() {
    float side1, side2, side3;

    cout << "Enter side 1: "; cin >> side1;
    cout << "Enter side 2: "; cin >> side2;
    cout << "Enter side 3: "; cin >> side3;

    // Validation: Triangle Inequality Theorem
    if (side1 + side2 > side3 && side1 + side3 > side2 && side2 + side3 > side1) {
        
        if (side1 == side2 && side2 == side3) {
            cout << "Result: Equilateral triangle." << endl;
        } 
        else if (side1 == side2 || side1 == side3 || side2 == side3) {
            cout << "Result: Isosceles triangle." << endl;
        } 
        else {
            cout << "Result: Scalene triangle." << endl;
        }
    } else {
        cout << "Error: Not a valid triangle." << endl;
    }

    return 0;
}

Console Output:

Enter side 1: 5
Enter side 2: 5
Enter side 3: 8
Result: Isosceles triangle.

Keywords & Concepts

Objectives

Example C++ Code

Console Output:

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