Re: Bug? Analytical integration of cosines gets the sign wrong
- To: mathgroup at smc.vnet.net
- Subject: [mg107194] Re: Bug? Analytical integration of cosines gets the sign wrong
- From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
- Date: Fri, 5 Feb 2010 03:22:19 -0500 (EST)
- References: <hkeb9k$b5$1@smc.vnet.net>
I get the same on my winxp32 machine. Looks like a bug to me... Cheers -- Sjoerd On Feb 4, 1:33 pm, K <kgs... at googlemail.com> wrote: > Hello everyone, > > the analytical integration in Mathematica 7.01.0 on Linux x86 (64bit) > > faultyInt = > Integrate[Cos[ph]*1/Pi*Cos[4*ph]*Cos[2*ph], {ph, Pi, 3/2*Pi}] > > gives as result: > > 19/(105 \[Pi]) > > which is as a decimal number > > N[faultyInt] > > 0.0575989 > > The numerical integration > > NIntegrate[Cos[ph]*1/Pi*Cos[4*ph]*Cos[2*ph],{ph,Pi,3/2*Pi}] > > gives > > -0.0575989 > > which I believe is correct by judging from the plot > > Plot[Cos[ph]*1/Pi*Cos[4*ph]*Cos[2*ph], {ph, Pi, 3/2*Pi}, > PlotRange -> {-1/Pi, 1/Pi}] > > and because the quadgk function in another system gives the same > negative result. Could anyone try this at home (or work, rather) > and confirm or disprove it? > Thanks, > K.