The figure formed by joining the mid-points of the sides of a quadrilateral ABCD, taken in order, is a square only if,
(A) ABCD is a rhombus
(B) diagonals of ABCD are equal
(C) diagonals of ABCD are equal and perpendicular
(D) diagonals of ABCD are perpendicular.
Given: ABCD is a quadrilateral and P, Q, R and S are the midpoints of sides of AB, BC, CD and DA. Then, PQRS is a square
…..(1)
Also, and
Thus all sides are equal.
Hence ABCD is either a square or a rhombus.
In by mid-point theorem
…..(2)
Similarly in …..(3)
From equation 1
Thus ABCD is a square so diagonals of a quadrilateral are also perpendicular.
Therefore option (C) is correct.