verify the identity: tanxcos(squared)x=[(2tanxcos(squared)x-tanx)/(1-tan(squared)x]
hehe, i was thinking the same thing, haha. it seems i have been picking on you a lot tonight, huh?
don't worry about it, when i just started here, the same thing happened to me. just look through some of my old posts, i was constantly making a fool of myself (i still do sometimes).
it's tough love. i have nothing against you. trust me, it will help you in the long run. if you feel like someone's always there to critique you, you'll start to think things through more carefully.
Power to you!
the most important thing you will need to know is the fraction $\displaystyle \frac{cos(x)}{sin(x)}=cot(x)$ is made by[ math]\frac{cos(x)}{sin(x)}=cot(x)[/math but i took off the ] after /math...look up LaTeX if you plan on using this site often it is a neccessity to learn
see the tutorial here for how to use LaTeX
i will start you off.
Consider the RHS:
$\displaystyle \displaystyle \frac {2 \tan x \cos^2 x - \tan x}{1 - \tan^2 x} = \tan x \cdot \frac {2 \cos^2 x - 1}{1 - \frac {\sin^2 x}{\cos^2 x}}$
$\displaystyle \displaystyle = \tan x \cdot \frac {2 \cos^2 x - 1}{\frac {\cos^2 x - \sin^2 x}{\cos^2 x}}$
$\displaystyle = \frac {\sin x}{\cos x} \cdot {\color{red}2 \cos^2 x - 1} \cdot \frac {\cos^2 x}{{\color{red}\cos^2 x - \sin^2 x}}$
now what? (of course, i put the two things in red for a reason)