Square

All sides are equal and each angle is 90 .

                                                               or

Square is a rectangle in which is all sides are equal.

                

AB=BC=CD=DA  (All sides are equal)

<A = <B = <C = <D = 90

AD = BC ( Diagonals are equal)

Area of square = (side)*(side) = (side)²

perimeter of square = 4 (side)

 diagonal of square =  √2 (side)

                   diagonal BC =  √2 (side)