If $$\int \frac{1+x^2}{1+x^4} d x=\frac{1}{\sqrt{2}} \tan ^{-1}\left[\frac{f(x)}{\sqrt{2}}\right]+c$$, then $$f(x)=$$

$$\int \frac{x+\sin x}{1+\cos x} d x=$$

$$\int \sin ^{-1} x d x=$$

$$\int \log x \cdot(\log x+2) d x=$$