Inverse trigonometric function of a double-angle expression: reduce to 2 tan^-1 x, then integrate by parts

1. A.
   $2x\tan^{-1}x - \log(1+x^2) + c$
2. B.
   $2x\tan^{-1}x + \log(1+x^2) + c$
3. C.
   $x\tan^{-1}x + \log(1+x^2) + c$
4. D.
   $2x\tan^{-1}x - \log(1+x^2) + c$ [same as A]

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1. A.
   $2x\tan^{-1}3x + \dfrac{1}{3}\log(1 + 9x^2) + c$
2. B.
   $2x\tan^{-1}3x - \log(1 + 9x^2) + c$
3. C.
   $2x\tan^{-1}3x - \dfrac{1}{3}\log(1 + 9x^2) + c$
4. D.
   $x\tan^{-1}3x + \dfrac{1}{3}\log(1 + 9x^2) + c$

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