# Integrate : $\int \sec^2 x \log (\tan x) .dx$

$(a)\;\tan x [\tan x -1]+c \\(b)\; \cos x[\cos x-1]+c\\(c)\;\sin x [\sin x-1]+c \\ (d)\;None$

$\tan x=t$
By differentiate with respect to x
$\sec^2 x dx =dt$
$\int 1. \log t .dt$