Re: Compute ArcTan(n Pi+ Pi/2 + O(1))

*To*: mathgroup at smc.vnet.net*Subject*: [mg95902] Re: Compute ArcTan(n Pi+ Pi/2 + O(1))*From*: dimitris <dimmechan at yahoo.com>*Date*: Thu, 29 Jan 2009 05:57:38 -0500 (EST)*References*: <glpfdv$kje$1@smc.vnet.net>

On 28 =C9=E1=ED, 13:26, Franc... at news.free.fr, Fay... at news.free.fr wrote: > Hello, > > I'm new to Mathematica and I want to compute a serie expantion of > > ArcTan(n Pi + Pi/2 + O(1)) (The O is a big O and is taken when n goes > to Infinity) > > I dont know how to input O(1) in Mathematica. For example > O[n,Infinity]^0 simplifies to 1 which is not what I want. > > Thanks for the help. > Francois O(1) in Mathematica is O[x]^1. So for exaple In[5]:= ArcTan[n*Pi + Pi/2 + O[n]^1] // InputForm Out[5]//InputForm= SeriesData[n, 0, {ArcTan[Pi/2]}, 0, 1, 1] In[6]:= ArcTan[n*Pi + Pi/2 + O[n]^3] // InputForm Out[6]//InputForm= SeriesData[n, 0, {ArcTan[Pi/2], (4*Pi)/(4 + Pi^2), -Pi^3/(2*(1 + Pi^2/4)^2)}, 0, 3, 1] etc Dimitris