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 you say about the quadrilateral, PQRS?
Parallelogram
Draw the diagonals of the parallelogram as shown in the figure below:
From mid-point theorem:
In △ABD,
SP∥BD and
SP=12BD ... (i)
In △BCD,
QR∥BD and
QR=12BD ... (ii)
In △ABC,
PQ∥AC and
PQ=12AC ... (iii)
In △ADC,
RS∥AC and
RS=12AC ... (iv)
Therefore, SP=QR [from (i) and (ii)]
and PQ=RS [from (iii) and (iv)]
Since, the opposite sides are equal and parallel. So, PQRS is a parallelogram.
We need to check whether one of the angles is 90∘ or not to determine if PQRS is a rectangle or not.
Since, RS∥AC and QR∥BD, ∠AOB=∠SRQ
We know that diagonals, AC and BD bisect each other and do not intersect at right angles.
Therefore, PQRS is a parallelogram and not a rectangle.