# What is the derivative of arctan(x/a)?

$\frac{d}{\mathrm{dx}} \left[\arctan \left(\frac{x}{a}\right)\right] = \frac{\frac{1}{a}}{1 + {\left(\frac{x}{a}\right)}^{2}} = \frac{1}{a \left(1 + {\left(\frac{x}{a}\right)}^{2}\right)}$
$\frac{d}{\mathrm{dx}} \left[\arctan \left(\frac{x}{a}\right)\right] = \frac{\frac{1}{a}}{1 + {\left(\frac{x}{a}\right)}^{2}} = \frac{1}{a \left(1 + {\left(\frac{x}{a}\right)}^{2}\right)}$