\(ABCD\) is a quadrilateral in which \(AD = BC\) and \(∠ DAB = ∠ CBA\).
 
Prove that:
 
(i) \(∆ ABD ≅ ∆ BAC\)
 
(ii) \(BD = AC\)
 
(iii) \(∠ ABD = ∠ BAC\).
 
Screenshot_14.png
 
Proof
 
(i) Considering two triangles \(ΔABD\) and \(ΔBAC\).
 
Here, \(AD =\) [Given] ----(1)
 
\(∠ DAB = ∠\) [Given] ---(2)
 
\(AB=AB\) [Common side] ---(3)
 
Therefore, by congruence rule\(ΔABD ≅ ΔBAC\)
 
Hence, we proved.
 
 
(ii) Since \(ΔABD ≅ Δ\) [By SAS Congruence rule]
 
So, by , \(BD = AC\) 
 
Hence, we proved.
 
 
(iii) Since \(ΔABD ≅ ΔBAC\) [By SAS Congruence rule]
 
So, by \(∠ABD = ∠BAC\)
 
Hence, we proved.