If $$\int_e^x t f(t)\, dt = \sin x - x \cos x - \dfrac{x^2}{2}$$, for all $$x \in R - \{0\}$$, then the value of $$f\left(\dfrac{\pi}{6}\right)$$ is

A

$$1/2$$

B

1

C

0

D

$$-1/2$$