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: [mg82772] Re: Bug of Integrate
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Tue, 30 Oct 2007 05:47:46 -0500 (EST)
  • Organization: The Open University, Milton Keynes, UK
  • References: <fg4dfv$6c3$1@smc.vnet.net> <fg6pse$d44$1@smc.vnet.net>

David W.Cantrell wrote:

<snip>

> However, related to the above, version 5.2 does give an incorrect result
> for a definite integral with a symbolic real limit. Whether this error
> still exists in version 6, I don't know:
> 
> In[3]:= Assuming[Element[x,Reals],Integrate[3*Sign[Cos[t]],{t,0,x}]]
> 
> Out[3]= 3 If[x > 0, x Abs[Cos[x]] Sec[x],
> Integrate[Sign[Cos[t]], {t, 0, x}, Assumptions -> x <= 0]]
> 
> The above is incorrect for x > Pi/2. A correct result would have been
> 
> 3 Sign[Cos[x]] (x - Pi Floor[x/Pi + 1/2])
> 
> for all real x.

Hi David,

Things have improved in version 6.0.1.

In[1]:= Assuming[Element[x, Reals],
  Integrate[3*Sign[Cos[t]], {t, 0, x}]]

Out[1]= 3 If[-(\[Pi]/2) <= x <= \[Pi]/2, x,
   Integrate[x Sign[Cos[t x]], {t, 0, 1},
    Assumptions ->
     x \[Element] Reals && ! -(\[Pi]/2) <= x <= \[Pi]/2]]

In[2]:= $Version

Out[2]= "6.0 for Microsoft Windows (32-bit) (June 19, 2007)"

Best regards,
-- 
Jean-Marc


  • Prev by Date: "Accumulate" in Mathematica 6
  • Next by Date: v6: Sloppy eps/pdf vector-format export compared to v5?
  • Previous by thread: Re: Bug of Integrate
  • Next by thread: Re: Bug of Integrate