1.
limx0+xsin1(2x1+x2)cos1(1x21+x2)tan1(3xx313x2)\displaystyle\lim_{x\to0^+}\frac{x\sin^{-1}\left(\frac{2x}{1+x^2}\right)}{\cos^{-1}\left(\frac{1-x^2}{1+x^2}\right)\tan^{-1}\left(\frac{3x-x^3}{1-3x^2}\right)} is equal to