2. Two-dimensional shapes
2.1 Quadrilaterals (shapes with four straight sides) and triangles (shapes with three straight sides)
Shape | Perimeter | Area | |
Square (all sides equal and opposite sides parallel, all angles right angles) |
4 x | x^{2} | |
Rectangle |
2 (x + y) | xy | |
Parallelogram (see also note below) |
2 (x + y) | xh | |
Trapezium |
x + y + a + b | h (y + 0.5 (x -y)) | |
Triangle (three sides: special cases where all sides equal = equilateral; and two sides equal = isosceles) |
x + y + z | 0.5 hz |
Note: a parallelogram where all four sides are equal is called a rhombus