Differentiating $\tan\left(\frac{1}{ x^2 +1}\right)$ Differentiate: $\displaystyle \tan \left(\frac{1}{x^2 +1}\right)$
Do I use the quotient rule for this question? If so how do I start it of?

$\displaystyle \frac d {dx}\tan\frac 1 {1+x^2}$
$\displaystyle=\left(\frac d {du} \tan u\right)\left(\frac d {dx}\frac 1 {1+x^2}\right)$ [Chain rule]
$=\cdots$ [Quotient rule]
