Let ABCD is a quadrilateral in which P, Q, R and * are midpoints of sides AB, BC, CD and DA respectively join PQ, QR, RS, SP and BD
In ΔABD, * and P are the midpoints of AD and AB respectively.
So, by using midpoint theorem we can say that
As in quadrilateral SPQR one pair of opposite side are equal and parallel to each other.
So, SPQR is parallelogram
Since, diagonals of a parallelogram bisect each other.
Hence PR and QS bisect each other.
