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