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Re: Bug of Integrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82742] Re: Bug of Integrate
  • From: Peter Pein <petsie at dordos.net>
  • Date: Tue, 30 Oct 2007 03:29:48 -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?
> 
> 

Hi Miguel,

I do not know, how you simplified the expression, but i get (with
Sqrt[z^2]==Abs[z]):

Sqrt[1/Cos[t]^2]*3*Cos[t] = 3*Sign[Cos[t]]

and the Integral is 0 (which Version 5.2 calculates correctly).

Peter


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