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Areas Of Parallelograms And Triangles

Question
CBSEENMA9002555

ABCD is a quadrilateral in which AD = BC and ∠DAB = ∠CBA (see figure). Prove that:



(i) ∆ABD ≅ ∆BAC
(ii) BD = AC
(iii) ∠ABD = ∠BAC.

Solution

Given: ABCD is a quadrilateral in which AD = BC and ∠DAB = ∠CBA.
To Prove: (i) ∆ABD ≅ ∆BAC
(ii)    BD = AC
(iii)    ∠ABD = ∠BAC.
Proof: (i) In ∆ABD and ∆BAC,
AD = BC    | Given
AB = BA    | Common
∠DAB = ∠CBA    | Given
∴ ∆ABD ≅ ∠BAC    | SAS Rule
(ii)    ∵ ∆ABD ≅ ∆BAC    | Proved in (i)
∴ BD = AC    | C.P.C.T.
(iii)    ∵ ∆ABD ≅ ∠BAC    | Proved in (i)
∴ ∠ABD = ∠BAC.    | C.P.C.T.

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