Write the given trigonometric function in terms of $\cos x$.
$\tan x$

$\pm \frac{\sqrt{1+{\cos }^{2}x}}{\cos x}$

$\pm \frac{\sqrt{{\cos }^{2}x-1}}{\cos x}$

$\pm \frac{\sqrt{1-{\cos }^{2}x}}{1+{\cos }^{2}x}$

$\pm \frac{\sqrt{1-{\cos }^{2}x}}{\cos x}$