The frictional torque transmitted in a conical pivot bearing considering uniform pressure is : (R: radius of shaft,a : semi angle of cone, $$\mu$$ : Coefficient of friction, W: load on bearing)

A

$$\left(\frac{1}{2}\right)\mu WR \cosec \alpha$$

B

$$\left(\frac{3}{4}\right)\mu WR \cos \alpha$$

C

$$\left(\frac{2}{3}\right)\mu WR \cos \alpha$$

D

$$\left(\frac{2}{3}\right)\mu WR \cosec \alpha$$