1.

In the figure ABCD is a trapezium in which side AB is parallel to side DC and E is the midpoint of side AD. If F is a point on the side BC such that the line segment EF is parallel to DC.Prove that Fis the mid-point of BC and `EF =1/2 (AB+DC)`

Answer» in `/_ ADC`
`(AE)/(ED) = (AM)/(MC)`
`M` is the mid point of AC
`AB || DC || EF`
`EF || DC`
`EM || DC`
so,`AB || EF`
`AB || MF`
`F ` is also a mid point of BC
as M is the mid point of AD
`(AM)/(MD) = (BF)/(FD)`
`EM = 1/2 DC`
`=> AB || QR`
`AB = 1/2 QR`
If A&B are midpoints of PQ & PR
`E & M` are midpoints
`EM || DC & EM= 1/2(DC)`
& similarly, `MF = 1/2(AB)`
`EM + MF = 1/2[AB + CD]`
`EF= 1/2[AB + CD]`
hence proved


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