I have this identity in which i have to prove. Its supposed to be done by means of expanding the left side using sum and difference formulas and then simplifying down to tan x. Just can;t seem to figure it out. Thanks
recall, $\displaystyle \tan (x - y) = \frac {\tan x - \tan y}{1 + \tan x \tan y}$
apply this to the left hand side, then multiply the resulting expression by $\displaystyle \frac {1 + \tan x \tan y}{1 + \tan x \tan y}$. can you take it from there?
Last edited by mr fantastic; Jan 22nd 2009 at 06:07 PM.
Reason: No edit - just flagging the reply as having been moved from a duplicate post.