The bisectors of an angle B and angle C of an isosceles triangle ABC with AB=AC intersect each other

The bisectors of an angle B and angle C of an isosceles triangle ABC with AB=AC intersect each other at a point O . show that the exterior angle adjacent to angle ABC is equal to angle
BOC.
Class 9 Maths R S Agarwal, Chapter name - Triangle , Chapter number - 7, Question number - 21, Exercise -7.1
Class 9 Maths , RS Agarwal, Triangles.