A particle is released on a vertical smooth semicircular track from point X so that, OX makes angle $$\theta$$ from the vertical (see figure). The normal reaction of the track on the particle vanishes at the point Y where OY makes an angle $$\phi$$ with the horizontal. Then:

A

$$\sin\phi = \frac{2}{3}\cos\theta$$

B

$$\sin\phi = \frac{3}{4}\cos\theta$$

C

$$\sin\phi = \frac{1}{2}\cos\theta$$

D

$$\sin\phi = \cos\theta$$