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In the quadrilateral given below, AB || DC || EG. If E is mid-point of AD, prove that

(i) G is midpoint of BC

(ii) 2EG = AB + CD

In the quadrilateral, AB || DC || EG. E is mid-point of AD. Prove that (i) G is the mid-point of BC (ii) 2EG = AB + CD. Mid-point Theorem, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Mid-point Theorem

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Answer

(i) Given,

EG || AB, we can say that

⇒ EF || AB

In △DAB,

E is midpoint of AD and EF || AB

∴ F is midpoint of BD (By converse of mid-point theorem).

EF = 12\dfrac{1}{2}AB …….(1)

Given,

EG || DC we can say that,

FG || DC

In △BCD,

F is midpoint of BD and FG || DC

∴ G is midpoint of BC (By converse of mid-point theorem).

Hence, proved that G is midpoint of BC.

(ii) In △BCD,

F is midpoint of BD and G is midpoint of BC

∴ FG = 12\dfrac{1}{2}DC …….(2)

Adding eqn. 1 from part (i) and eqn. 2 we get,

EF + FG = 12\dfrac{1}{2}AB + 12\dfrac{1}{2}DC

EG = 12\dfrac{1}{2}(AB + CD)

2EG = AB + CD.

Hence, proved that 2EG = AB + CD.

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