Revision sheet · Mathematics

Perimeter and area of flat shapes

Perimeter of a rectangle: $P = 2 (l + b)$
Area of a rectangle: $A = l b$
Area of a triangle (half base times height): $A = \frac{1}{2} bh$
Area of a parallelogram: $A = bh$
Heron's formula (area of a triangle from its sides): $A = s (s - a) (s - b) (s - c)$
Brahmagupta's formula (area of a cyclic quadrilateral): $A = (s - a) (s - b) (s - c) (s - d)$