In a circle with centre O, AD is a diameter and AC is a chord. Point B is on AC such that OB = 7 cm and ∠OBA = 60°. If ∠DOC = 60°, then what is the length of BC?

Solution (By Examveda Team)

$$\eqalign{ & OB = 7\,{\text{cm}} \cr & {\text{Sine Rule in }}\Delta BOC \cr & \frac{{OB}}{{\sin {{30}^ \circ }}} = \frac{{BC}}{{\sin {{30}^ \circ }}} \cr & BC = 7\,{\text{cm}} \cr} $$