To prove that DE is parallel to BC,
if we prove that angle ADE = Angle ABC , hence it will be proved because of corresponding angle property
so we will prove it first
∠B = ∠C .... (1)
In the cyclic quadrilateral CBDE, side BD is produced to A.
We know that exterior angle is equal to opposite interior angle.
i.e. ∠ADE = ∠C .... (2)
From (1) and (2) –
∠ADE = ∠ABC
SO corresponding angles are equal
Ans hence DE is parrallel to BC