1.

Prove that the straight lines joining the mid-points of the opposite sides of a parallelogranare parallel to the other pairs of parallel sides.14.

Answer»

Let us have a parallelogram ABCD , and E and F are mid points of AB and CD respectively .

Here Diagonals AC and BD and EF intersect at " O " .

We know diagonals of parallelogram bisect each other , So

AO = CO

In∆ABC , we have

AE = BE , as we assumed E is mid point of ABAndAO = CO , from property of parallelogram .SO,From conserve of mid point theorem , we get

EO | | BC , SO

EF | | BC ( As EO is part of line EF )

AndWe know BC | | DA , from property of parallelogram , So

We can say

BC | | DA | | EFSo,Joining the mid points of the opposite sides of a parallelogram are parallel to the other pairs of parallel sides. ( Hence proved )



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