If $$\frac{d}{dx}\left[\frac{(x^{2}+1)\sin x}{(\log x)(\sec x)}\right]= f(x)\left[\frac{2x}{x^{2}+1}+\cot x - \frac{1}{x \log x} - \tan x\right]$$, then $$f(x) = $$

A

$$\left[\frac{(x^{2}+1)\sin x}{(\log x)(\sec x)}\right]$$

B

$$(x^{2}+1)\sin x - (\log x)\sec x$$

C

$$(\log x)(\sec x) - (x^{2}+1)\sin x$$

D

$$\frac{(x^{2}+1)\sin x-2x \cos x}{\log x \sec x-\sec x \tan x}$$