Question: abcd is a rectangle in which diagonal ac bisects  a and  c. prove that abcd is square?
Answer: Given: The diagonals AC and BD of a quadrilateral ABCD are equal and bisect each other at right angles. To Prove: Quadrilateral ABCD is a square. ∴ AD = CB | C.P.C.T. ∠ODA = ∠OBC | C.P.C.T.