NCERT Solutions
Class 9 Maths
Quadrilaterals

Ex.8.2 Q.3
ABCD is a rectangle and P, Q, R and S are mid-points of the sides AB, BC, CD and DA respectively.
Show that the quadrilateral PQRS is a rhombus.
Let us join AC and BD. In ∆ABC,
P and Q are the mid-points of AB and BC respectively.
So, PQ || AC and PQ = ………………………... (1)
(Mid-point theorem)
Similarly, in ∆ADC,
SR || AC and SR = ………………………………. (2)
(Mid-point theorem)
Clearly, PQ || SR and PQ = SR
Since in quadrilateral PQRS, one pair of opposite sides is equal and parallel to each other, it is a parallelogram.
PS || QR and PS = QR ………………………………... (3)
(Opposite sides of parallelogram)
In ∆BCD, Q and R are the mid-points of side BC and CD respectively.
QR || BD and QR = ………………………………. (4)
(Mid-point theorem)
However, the diagonals of a rectangle are equal.
So, AC = BD.………. (5)
By using equation (1), (2), (3), (4), and (5), we obtain
PQ = QR = SR = PS
Therefore, PQRS is a rhombus.