If two adjacent sides of a rectangle are equal, it is called a square. In the figure, ABCD is a square. A square has all the properties of a rectangle and the following additional property.
Property – All the sides of a square are equal in length.
Thus, every square is a rhombus and it has all the properties of a rhombus.
So, AC ⊥ BD, AC bisects ∠A and ∠C, and BD bisects ∠B and ∠D and
∆ OAB ≅ ∆ OBC ≅ ∆ OCD ≅ ∆ ODA