Question

ABCD is a quadrilateral in which AD = BC and ∠DAB = ∠CBA. Prove that
(i) ΔABD ≅ ΔBAC
(ii) BD = AC
(iii) ∠ABD = ∠BAC.

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Answer 1

Answer:

ABCD is a quadrilateral, where AD=BC and ∠DAB=∠CBA

In △ABD and △BAC,

⇒ AD=BC [ Given ]

⇒ ∠DAB=∠CBA [ Given ]

⇒ AB=BA [ Common side ]

∴ △ABD≅△BAC [ SAS Congruence rule ]

∴ ∠ABD=∠BAC [ CPCT ]

Answer 2

Answer:

Solution:

As per given in the question,

∠DAB = ∠CBA and AD = BC.

(i) ΔABD and ΔBAC are similar by SAS congruency as

AB = BA (common arm)

∠DAB = ∠CBA and AD = BC (given)

So, triangles ABD and BAC are similar

i.e. ΔABD ≅ ΔBAC. (Hence proved).

(ii) As it is already proved,

ΔABD ≅ ΔBAC

So,

BD = AC (by CPCT)

(iii) Since ΔABD ≅ ΔBAC

So, the angles,

∠ABD = ∠BAC (by CPCT).