A triangle is always half the area of a rectangle with the same height and width. To calculate the area of a triangle, multiply the height by the width (this is also known as the 'base') then ...

The base and the perpendicular height are at right angles to each other. The measurements used must be in the same units. For example, to work in cm a 45 mm measurement would have to be converted ...

Rectangles, arches, and triangles are the most common shapes used to build big structures. What happens when you push the side of a rectangle? The rectangle is a wobbly, unstable shape.