Given is a triangle △ABC and points M and K on lines AB and CB such that AM=AC=CK. Prove that the length of the radius of the circumcircle of triangle △BKM is equal to the lenght OI, where O and I are centers of the circumcircle and the incircle of △ABC, respectively. Also prove that OI⊥MK. geometrycircumcircletrigonometryTriangle