Square:

Area = a x a = a²

Perimeter = 4a

Where a = side of a square

Rectangle:

Area = Length x breadth = l x b

Perimeter = 2l + 2b

Where l = length

b = breadth

Triangle:

Area =

Also area =

Where s =

Perimeter = a + b + c

Parallelogram:

Area = base (b)*height (h)

Perimeter = 2a + 2b

Trapezoid:

Area =

Perimeter = a + b + c + d

Circle:

Area =

Perimeter = 2

Regular polygon:

Area = n x area of each triangle

Perimeter = n x length of each side (a)

Where n = no. of sides