In isosceles triangle triangle ABC, AB=AC. The side BA is produced to D such that BA=AD. Prove that : ∠BCD=90∘.

In isosceles triangle triangle ABC, AB=AC. The side BA is produced to

1.	In isosceles triangle triangle ABC, AB=AC. The side BA is produced to D such that BA=AD. Prove that : ∠BCD=90∘.
Answer» In isosceles triangle triangle $A B C$ , $A B = A C$ . The side $B A$ is produced to $D$ such that $B A = A D$ . Prove that : $∠ B C D = 90^{\circ}$ .