C++ Program to Find Area of Triangle

To find the area of a triangle in C++, use the formula area = 0.5 * base * height and write a program that takes base and height as input and prints the area.

Examples

Inputbase = 4, height = 3

OutputArea of the triangle is 6

Inputbase = 10, height = 5

OutputArea of the triangle is 25

Inputbase = 0, height = 5

OutputArea of the triangle is 0

How to Think About It

To find the area of a triangle, you need to know its base and height. The area is half the product of base and height. So, multiply base and height, then divide by 2 to get the area.

Algorithm

1

Get the base of the triangle from the user

2

Get the height of the triangle from the user

3

Calculate area by multiplying base and height, then dividing by 2

4

Display the calculated area

Code

cpp

#include <iostream>
using namespace std;

int main() {
    double base, height, area;
    cout << "Enter base of the triangle: ";
    cin >> base;
    cout << "Enter height of the triangle: ";
    cin >> height;
    area = 0.5 * base * height;
    cout << "Area of the triangle is " << area << endl;
    return 0;
}

Output

Enter base of the triangle: 4
Enter height of the triangle: 3
Area of the triangle is 6

Dry Run

Let's trace the example where base = 4 and height = 3 through the code

1

Input base

User enters base = 4

2

Input height

User enters height = 3

3

Calculate area

area = 0.5 * 4 * 3 = 6

4

Output area

Prints 'Area of the triangle is 6'

Step	Base	Height	Area
Input	4	-	-
Input	4	3	-
Calculate	4	3	6
Output	4	3	6

Why This Works

Step 1: Input base and height

The program asks the user to enter the base and height values using cin.

Step 2: Calculate area

It calculates the area using the formula 0.5 * base * height, which is the standard formula for triangle area.

Step 3: Display result

Finally, it prints the calculated area using cout so the user can see the result.

Alternative Approaches

Using Heron's formula

cpp

#include <iostream>
#include <cmath>
using namespace std;

int main() {
    double a, b, c, s, area;
    cout << "Enter sides a, b, and c: ";
    cin >> a >> b >> c;
    s = (a + b + c) / 2;
    area = sqrt(s * (s - a) * (s - b) * (s - c));
    cout << "Area of the triangle is " << area << endl;
    return 0;
}

This method calculates area using all three sides and is useful when height is unknown but sides are known.

Using base and height as integers

cpp

#include <iostream>
using namespace std;

int main() {
    int base, height;
    cout << "Enter base and height: ";
    cin >> base >> height;
    double area = 0.5 * base * height;
    cout << "Area of the triangle is " << area << endl;
    return 0;
}

This uses integer inputs but calculates area as double for precision.

Complexity: O(1) time, O(1) space

Time Complexity

The program performs a fixed number of arithmetic operations and input/output steps, so it runs in constant time.

Space Complexity

It uses a few variables to store inputs and the result, so space usage is constant.

Which Approach is Fastest?

Both base-height formula and Heron's formula run in constant time, but base-height is simpler and faster since it uses fewer operations.

Approach	Time	Space	Best For
Base and Height Formula	O(1)	O(1)	When base and height are known
Heron's Formula	O(1)	O(1)	When all three sides are known