First of all, the series for is incorrect.
Substitution will give you the Taylor series about . Is it the Maclaurin series that you're looking for? If so, you need to differentiate and evaluation at 0.
What is the quickest method to do this Taylor expansion for the first three terms? Somebody previously suggested doing the expansion for tan(x) and then substituting in (x + pi/4) but if I do that I get the following working and run into problems:
Thanks in advance.