Question

if angle BAC is 30 then find the value of angle BCA

Answer 1

30° will be the answer.

Answer 2

In triangle AOB and COB,
Angle AOB= Angle COB (90 each)
OB=OB (common)
AO=OC (radii)
Therefore triangles are congruent by SAS criterion.
This implies Angle OAB= angle OCB by CPCT.
i.e. Angle OCB=30.