A square is a quadrangle in which all angles and all sides are equal. A square is both a special case of a rhombus and a rectangle. Geometric properties of a square: the length of all sides is equal, the angles are all equal. The diagonals of the square are equal, mutually perpendicular, the intersection point is halved and are the bisectors of the angles. The formula for finding the area of a square knowing the length of a side: multiply any side by two. Knowing the diagonal: multiply one second by the length of the diagonal squared.