To calculate the area of a triangle, we first need to understand how to calculate the area of a rectangle.
The area of this 3×5 rectangle is simply , if we suppose the dimensions have been given in meters.
The formula to calculate the area of a rectangle is
The area of the triangle of the same rectangle is half the area of the rectangle, i.e.:
So the formula for area of a triangle is
In this example, it would be
Even if the triangle is not a right-angled triangle, it is still half of a rectangle, i.e.:
So the formula is still
In the above example, it would be
Remember to use the Height though, and NOT the length of one of the sides!