Question

If $y=\log \tan x,$ find $dy/dx$. at $x=\pi /4$

Answer 1

$y=\log \tan x$
$\Rightarrow \frac{dy}{dx}=\frac{1}{\tan x}.{\sec }^{2}x=2co\sec 2x.$
$\therefore$ at $x=\frac{\pi }{4}$, $\frac{dy}{dx}=2$