A small block starts slipping down from a point B on an inclined plane AB, which is making an angle $$\theta$$ with the horizontal section BC is smooth and the remaining section CA is rough with a coefficient of friction $$\mu$$. It is found that the block comes to rest as it reaches the bottom (point A) of the inclined plane. If $$BC = 2AC$$, the coefficient of friction is given by $$\mu = k \tan\theta$$. The value of $$k$$ is ___________.