Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Bug of Integrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82759] Re: Bug of Integrate
  • From: Szabolcs Horvát <szhorvat at gmail.com>
  • Date: Tue, 30 Oct 2007 03:38:33 -0500 (EST)
  • References: <fg4dfv$6c3$1@smc.vnet.net>

Miguel wrote:
> 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?

Simplifying it does not result in 3 :

In[1]:= Simplify[Sqrt[1/Cos[t]^2]*3*Cos[t]]
Out[1]= 3 Cos[t] Sqrt[Sec[t]^2]

In[2]:= Simplify[Sqrt[1/Cos[t]^2]*3*Cos[t], Element[t, Reals]]
Out[2]= 3 Abs[Sec[t]] Cos[t]

which is just 3 Sign[Cos[t]], and the value of the integral should be 0.

-- 
Szabolcs


  • Prev by Date: Setting Negatives to Zero
  • Next by Date: Re: Polar Plot
  • Previous by thread: Re: Bug of Integrate
  • Next by thread: Re: Bug of Integrate