A quadrilateral in which all the angles are right angles and all the sides are congruent.

### Properties

Its two diagonal lines are congruent and intersect at right angles.

Its opposite sides are parallel and its adjacent sides are perpendicular.

The square has four lines of symmetry and one centre of symmetry.

The square is an equilateral and equiangular.

The properties of a square place it in the family of convex quadrilaterals, trapezoids, parallelograms, rectangles and rhombuses.

### Formulas

The perimeter *P* of a square with side length *c* is : \(P=4c\).

The area *A* of a square with side length *c* is : \(A=c\times c\)

The formula for calculating the radius *r* of the circle circumscribed about a square is : \(r=\frac{c}{2}\sqrt{2}\)

The formula for calculating the radius *r* of the circle inscribed in a square is :\(r=\frac{c}{2}\)