Question 610011
the segments are tangent, so they are perpendicular to a radius at the points of tangency, A and C


OB is the hypotenuse of the two congruent right triangles formed by BA, BC and the radii at A and C


the two right triangles are congruent by hypotenuse-leg (OB and the two radii)


BA and BC are congruent by CPCTC