Side of a square: \(a\)

Diagonal of a square: \(d\)

Radius of the circumscribed circle: \(R\)

Radius of the inscribed circle: \(r\)

Diagonal of a square: \(d\)

Radius of the circumscribed circle: \(R\)

Radius of the inscribed circle: \(r\)

Perimeter: \(P\)

Area: \(S\)

Area: \(S\)

- A square is a regular quadrilateral. It has four equal sides and four equal angles (\(90^\circ\) angles).
- Diagonal of a square

\(d = a\sqrt 2\) - Radius of the circumscribed circle

\(R = d/2 =\) \(a\sqrt 2/2\) - Radius of the inscribed circle

\(r = a/2\) - Perimeter of a square

\(P = 4a\) - Area of a square

\(S = {a^2} = {\large\frac{{{d^2}}}{2}\normalsize} =\) \( 2{R^2} = 4{r^2}\)