Ex 7.2 QNo 6, ABC is isosceles with AB=AC, side BA is produced to D such that AD=AB.Show that BCD=90

Ex 7.2 Q No 6, triangle ABC is an isosceles triangle in which AB=AC, side BA is produced to D such that AD=AB.Show that angle BCD=90.

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But whaha 2 common hai 3 bhi to hai to three kyu bahar nahi aaya