# Square

A square is a quadrilateral having four sides of equal length. All its four angles are 90^{0}.

A square with the vertices (corners) A,B,C and D is usually written this way:

◻ABCD

## The area of a square

The area of a square is given by the formula:

where a is the side length.

A square is the quadrilateral having the greatest area in relation to its circumference.

## The circumference of a square

The circumference of a square is given by the formula:

where a is the side length.

## Calculate area and circumference of a square

## The inscribed circle

The inscribed circle of a square is a circle, the periphery of which touches all four sides of the square but never crosses to the outside of the square. The area of the inscribed circle is given by:

## The circumscribed circle

The circumscribed circle of a square is a circle, the periphery of which touches all four vertices of the square but never crosses to the inside of the square. The area of the circumscribed circle is given by: