$$|\cos(\ln x)-2\sin(\ln x)| \le |\cos(\ln x)|-|2\sin(\ln x)|$$
I'm confusing with $$|x-y|\ge||x|-|y||$$
because if I put minus in to $\sin(\ln x)$
It would be $$|\cos(\ln x)+2\sin(-\ln x)|\le|\cos(\ln x)|+|2\sin(-\ln x)|$$
Then it end up with $$|x+y|\le|x|+|y|$$