# Thread: series expansion of cotx

1. ## series expansion of cotx

hi you,

he expansion for the cosx ... okay got it

but though i can do the long division to get tanx i can't for the series expansion of cotx

maybe you know much more than me

yes?

2. Originally Posted by pepsi
hi you,

he expansion for the cosx ... okay got it

but though i can do the long division to get tanx i can't for this

maybe you know much more than me

yes?

there is not a general Taylor form for cotx and tanx you can find some terms by long division as you said but there is no general form that's it .

3. An expansion about the origin is:

$\cot(z)=\sum_{n=0}^{\infty}\frac{(-1)^n 2^{2n} B_{2n}}{(2n)!} z^{2n-1}$

where I assume the radius of convergence is up to the next pole.