Page 13 - Ans Sub

∠ABL = ∠LBC and ∠MCB = ∠MCD
⇒∠ABL = ∠MCD …(2) [By (1)]
Adding (1) and (2), we get
∠LBC + ∠ABL = ∠MCB + ∠MCD
⇒∠ABC = ∠BCD
i.e., a pair of alternate interior angles are equal.
∴ AB || CD.

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