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 to ...

The area of the rectangle is 8 cm 2. Two triangles make the rectangle. The area of one triangle is half the area of the rectangle. \(8 \div 2 = 4~\text{cm}^2\) The area of a triangle can also be ...