Find the derivative of $y=\sec \left(\tan x\right)$.

$y^{\prime }={\sec }^{2}x\sec \left(\tan x\right)\tan \left(\tan x\right)$

$y^{\prime }=\sec x\tan x$

$y^{\prime }=-\sec \left(\tan x\right)\tan \left(\tan x\right)$

$y^{\prime }=-\sec x\tan x$