In the given figure, AB = AC. Side BA is produced to D such that BA = AD. △BDC is _______.
90º
In △ABC, AB = AC ..... (given)
∠ABC = ∠ACB = ∠x (say) ....... (base angles of an isosceles △)
In △ACD, AC = AD ...(given, BA = AD and BA = AC)
∠ADC = ∠ACD = ∠y (say) ....... (base angles of an isosceles △)
In △ADC,
x° + x° + y° + y° = 180° ...... (sum of angles of a △)
2 (x° + y°) = 180°
x° + y° = 90°
∠DCB = 90°
△BDC is a right angle.