A quadrilateral ABCD is drawn in which the mid points of sides AB, BC, CD and AD are P, Q, R and S respectively.
If quadrilateral ABCD is a parallelogram, what can be said about sides SP and QR?
Equal and parallel
Join the diagonal BD of quadrilateral ABCD.
In ΔABD,
Since S is the mid-point of AD and P is the mid-point of AB, SP || BD and SP = 12 BD (mid point theorem) --- (i)
In ΔBCD,
Since R is the mid-point of DC and Q is the mid-point of BC,
QR || BD and QR = 12 BD (mid point theorem) ---(ii)
From (i) and (ii), SP || QR and
SP = QR ---(iii)
Thus, sides SP and QR are equal and parallel.