2-dimensional shapes are flat. The perimeter of a 2D shape is the total distance around the outside of the shape. The area of a 2D shape is the space inside the shape.
To calculate the area of a triangleThe simplest two-dimensional shape is the triangle, a three-sided shape with three angles., draw a second triangle to form a rectangle.
Example
The area of the rectangle is 8 cm2.
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 calculated using the formula: \(\text{area of a triangle} = \frac{\text{base} \times \text{height}}{2}\)