Calculate the area of a triangle

The area is how much space the triangle takes up. The base $b$ is the side the triangle stands on, and the height $h$ is the distance from the base straight up to the top corner.

The formula is:

$$A = \frac{1}{2} \cdot b \cdot h$$

You multiply the base by the height and take half. The reason is that a triangle is exactly half of a rectangle with the same base and height. The rectangle's area is $b \cdot h$, so the triangle's area is half of that.