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Re: Bug of Integrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82739] Re: Bug of Integrate
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Tue, 30 Oct 2007 03:28:09 -0500 (EST)
  • References: <fg4dfv$6c3$1@smc.vnet.net>

Miguel schrieb:
> When I try to calculate the integral
>
> Integrate[Sqrt[1/Cos[t]^2]*3*Cos[t],{t,0,2Pi}]  Mathematica 6.0.1
> yields -6*Pi.
>
> Simplifying the expresion resultrs Integrate[3,{t,0,2*Pi}] and It is
> clear that the correct solution is 6*Pi.
>
> Is a bug of Version 6.0.1?
>
The Integral should never be 6Pi but 0. Because your Integrand ist -3
in the Interval (-Pi/2, 3Pi/2) and +3 outside. If you simplify your
integrand you get the result correct result 0.

Your integand is effectively 3 Cos[t]/Abs[Cos[t]].

But I can't imagine, where the result -6Pi comes from. Must have to
do with the undefined values at t=Pi/2 and t=3Pi/2

Gruss Peter
-- 
==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de


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