Re: Real sum gives complex result -> Bug in Mathematica?
- To: mathgroup at smc.vnet.net
- Subject: [mg44513] Re: [mg44493] Real sum gives complex result -> Bug in Mathematica?
- From: "Bruce W. Colletti" <bcolletti at compuserve.com>
- Date: Thu, 13 Nov 2003 02:27:04 -0500 (EST)
- References: <200311121301.IAA12534@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Two related issues regarding Input [1]: - Load result into X and run Simplify[X,Trig -> True]. This returns a different expression that when hit with //N returns 4.44101 + 4.05328x10^15 I - Strike the replacement rule and hardwire d=10. (note the decimal) and n=100 to get 47.7141 Question for all: why does Mathematica 5.0 (running under WinXP Home) return these results? Bruce ----- Original Message ----- From: "Norbert Schuch" <nsng0203 at web.de> To: mathgroup at smc.vnet.net Subject: [mg44513] [mg44493] Real sum gives complex result -> Bug in Mathematica? > Hi, > > the following problems appears with Mathematica 4,0, 4.1, 4.2: > > > | In[1]:= Sum[Sin[Pi*k/n]*Sin[Pi*(k-d)/n],{k,d,n}]/.{d->10,n->100}//N > | > | Out[1]= 39.4497 - 25.4353 I > | > | In[2]:= Sum[Sin[Pi*k/n]*Sin[Pi*(k-d)/n],{k,d+1,n}]/.{d->10,n->100}//N > | > | -14 > | Out[2]= 47.7141 - 6.11986 10 I > | > | In[3]:= Sum[Sin[Pi*k/n]*Sin[Pi*(k-d)/n],{k,10,100}]/.{d->10,n->100}//N > | > | Out[3]= 47.7141 > > > Output 2 and 3 are correct, while output 1 is complex although the sum > is over real contributions! (The difference between 1 and 2 is zero, as > the second sine vanishes.) What is the problem? > > > Thanks, Norbert > > >
- References:
- Real sum gives complex result -> Bug in Mathematica?
- From: nsng0203@web.de (Norbert Schuch)
- Real sum gives complex result -> Bug in Mathematica?