If in a triangle ABC as drawn in the figure, AB = BC and ∠ACD = 130o, then ∠BAC is equal to :

60o 50o 70o 80o

50o

Concept Used Linear Pair theorem Angle sum property = Sum of all the angles of the triangle is 130o Calculation In triangle ABC, ∠ACD + ∠ACB = 180o        (Linear pair) ∠ACB = 180 - 130 = 50o Since AB = BC, Triangle ABC is an isosceles triangle. ∠ACB = ∠BAC = 50o Therefore,∠BAC is 50o.