This identity makes no sense to me:

cot(x) - tan(x) - tan(x) + cot(x) = (4 - 2sec^2(x))/tan(x)

I did this:

LS

=2cot(x) - 2tan(x)

=2{cot(x) - tan(x)}

=2[{1/tan(x)} - tan(x)]

=2[{1-tan^2(x)}/tan(x)]

=2{sec^2(x)}/tan(x)

Where did i go wrong? I don't have a "4-" term.

Please help...

ps. I used the different bracket types to differentiate from different sets of brackets. i'm sorry if it means something else in math...