Question:
Evaluate the following integrals:
$\int \frac{1+\tan x}{x+\log x \sec x} d x$
Solution:
Assume $x+\log x \sec x=t$
$d(x+\log x \sec x)=d t$
$1+\frac{\sec x \tan x}{\sec x} d x=d t$
$(1+\tan x) d x=d t$
Put $\mathrm{t}$ and $\mathrm{dt}$ in given equation we get
$\Rightarrow \int \frac{\mathrm{d} t}{t}$
$=\ln |t|+c$
But $t=x+\log x \sec x$
$=\ln |x+\log x \sec x|+c$