Question

If O is center of circle and angle CBO is 40° then what are values of angle BCO and
angle COB.

A) 90°, 50° B) 80°, 60° C) 70°, 70° D) 60° , 80° E) 50°, 90°

Answer 1

If any line drawn from center of the circle (OC in the diagram) bisect the chord of circle (AB in the diagram), then it is said to be perpendicular to chord AB.
So OC is perpendicular to CB, and we can say that triangle OCB is the Right Triangle.

In the Right Triangle OCB,
angle BCO = 90°
angle COB = 90° - angle CBO = 90° - 40° = 50°

So, option A is the final answer, 90° and 50°.

Answer 2

If any line drawn from center of the circle (OC in the diagram) bisect the chord of circle (AB in the diagram), then it is said to be perpendicular to chord AB.

So OC is perpendicular to CB, and we can say that triangle OCB is the Right Triangle.

In the Right Triangle OCB,

angle BCO = 90°

angle COB = 90° - angle CBO = 90° - 40° = 50°

So, option A is the final answer, 90° and 50