Show that the line segments joining the mid points of the opposite sides of a quadrilateral bisect each other.


To do:

We have to show that the line segments joining the midpoints of the opposite sides of a quadrilateral bisect each other.

Solution:

Let in a quadrilateral $ABCD$, $P, Q, R$ and $S$ are the midpoints of sides $AB, BC, CD$ and $DA$ respectively.

$PR$ and $QS$ intersect each other at $O$.

Join $PQ, QR, RS$ and $SP$ and join $AC$.


In $\triangle ABC$,

$P$ and $Q$ are mid-points of $AB$ and $BC$

This implies,

$PQ \parallel AC$ and $PQ = \frac{1}{2}AC$....…(i)

Similarly, 

In $\triangle ADC$,

$S$ and $R$ are the mid-points of $AD$ and $CD$

This implies,

$SR \parallel AC$ and $SR = \frac{1}{2}AC$......(ii)

From (i) and (ii), we get,

$PQ = SQ$ and $PQ \parallel SR$

Opposite sides are equal area parallel.

This implies,

$PQRS$ is a parallelogram.

The diagonals of a parallelogram bisect each other.

Therefore,

$PR$ and $QS$ bisect each other.

Hence proved.

Updated on: 10-Oct-2022

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