Why is the Area of a Triangle 1/2*b*h?

Omer Seyfeddin Koc
3 min readOct 6, 2024

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Mathematics is one of the fundamental sciences that appears in our daily lives, often without us realizing it. One of these mathematical concepts is the area of a triangle. The formula might seem simple, but it is based on a rather interesting logic. So, why is the area of a triangle calculated using the formula “base times height divided by 2”?

The Relationship Between a Rectangle and a Triangle

To understand a triangle, it is helpful to first understand a rectangle. The area of a rectangle is calculated by multiplying its length by its width:

Area = Length × Width

A triangle can be thought of as half of a rectangle. If you divide a rectangle diagonally from one corner to the opposite corner, you will create two equal triangles. Therefore, the area of each triangle is half of the rectangle’s area:

Area of the Triangle = Area of the Rectangle / 2

Now, if we consider the rectangle’s length as the base of the triangle and its width as the height of the triangle, the area formula becomes:

Area of the Triangle = (Base × Height) / 2

It’s also useful to understand the area of a triangle visually. Imagine dividing a rectangle diagonally to form two equal triangles. Each triangle will occupy exactly half of the rectangle. This means that the area of a triangle is always half the product of its base and height.

This simple yet powerful formula reveals the symmetry and nature of the triangle. When we move from abstract mathematical concepts to visual understanding, calculating the area of a triangle becomes much clearer.

Applying the Formula to Different Types of Triangles

This formula applies to all types of triangles: right triangles, isosceles triangles, equilateral triangles, or any random triangle. The key is to correctly identify the height. In right triangles, the base and height are the sides that form the right angle, making the calculation straightforward. For other types of triangles, determining the height can be more challenging because you need to draw a line perpendicular to the base.

Conclusion

The reason why we calculate the area of a triangle using “base times height divided by 2” is based on a simple visual logic and the relationship between rectangles and triangles. Many mathematical formulas might appear complicated, but the logic behind them is often simple and easy to grasp. This formula provides a universal way to calculate the area of any triangle in the world of geometry.

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