1.

`A B C D`is a parallelogram `X`and `Y`are the mid-points of `B C`and `C D`respectively. Prove that `a r( A X Y)=3/8a r(^(gm)A B C D)`GIVEN : A parallelogram `A B C D`in which `X`and `Y`are the mid-points of `B C`and `C D`respectively.TO PROVE : `a r( A X Y)=3/8a r(^(gm)a b c d)`CONSTRUCTION : Join `B Ddot`

Answer» `In /_BCD`
X and Y are midpoint of sides BC and CD
XY||BD and XY=1/2BD
`ar(/_CXY)=1/4*ar(/_ABC)`
`ar(/_CYX)=1/8*ar(paral l elogram ABCD)-(1)`
ParallelogramABCD and `/_ABX`
AD||BX
`BX=1/2BC`
`/_ABX=1/4(||gram ABCD)-(2)`
`ar(/_AYD)=1/4ar(||gram ABCD)-(3)`
`ar(||gram ABCD)=ar(/_ABX)+ar(/_AYB)+ar(CYX)+ar(/_AXY)`
`ar(AXY)=ar(||gram ABCD)-[ar(/_ABX)+ar(/_ATD)+ar(/_CYX)]`
`ar(/_AXY)=(1-5/8) ar(||gram ABCD)`
`ar(/_AXY)=3/8 ar(||gram ABCD)`.


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