Geometry Practice Test 6

AB is the diameter of a circle with the centre O.
∠AOP + ∠BOP = 180° {linear pair}
∠BOP = 180° - 120°
∠BOP = 60°

OP = OB = radius and ∠OBP = ∠OPB = x
In ΔPBO,
∠BOP + ∠OPB + ∠OBP = 180°
60° + x + x = 180
2x = 120
x = 60°
⇒ ∠PBO = 60°