show that the quadrilateral formed by joining the mid points of the adjacent sides of the of a square is a square
Answers
Answer:
In a square ABCD, P,Q,R and S are the mid-points of AB,BC,CD and DA respectively.
⇒ AB=BC=CD=AD [ Sides of square are equal ]
In △ADC,
SR∥AC and SR=
2
1
AC [ By mid-point theorem ] ---- ( 1 )
In △ABC,
PQ∥AC and PQ=
2
1
AC [ By mid-point theorem ] ---- ( 2 )
From equation ( 1 ) and ( 2 ),
SR∥PQ and SR=PQ=
2
1
AC ---- ( 3 )
Similarly, SP∥BD and BD∥RQ
∴ SP∥RQ and SP=
2
1
BD
and RQ=
2
1
BD
∴ SP=RQ=
2
1
BD
Since, diagonals of a square bisect each other at right angle.
∴ AC=BD
⇒ SP=RQ=
2
1
AC ----- ( 4 )
From ( 3 ) and ( 4 )
SR=PQ=SP=RQ
We know that the diagonals of a square bisect each other at right angles.
∠EOF=90
o
.
Now, RQ∥DB
RE∥FO
Also, SR∥AC
⇒ FR∥OE
∴ OERF is a parallelogram.
So, ∠FRE=∠EOF=90
o
(Opposite angles are equal)
Thus, PQRS is a parallelogram with ∠R=90
o
and SR=PQ=SP=RQ
∴ PQRS is a square.
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