Thread: Help with a trig identity

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...

Hello, CenturionMonkey!

I did this:



. . . . . . no

We have: .

Therefore: .

Oh right! cause 1 + tan^2(x) = sec^2(x).

thanks a lot