Re: Assumptions ignored?

• To: mathgroup at smc.vnet.net
• Subject: [mg25109] Re: Assumptions ignored?
• From: Mark Fisher <mark.fisher at atl.frb.org>
• Date: Sun, 10 Sep 2000 03:14:32 -0400 (EDT)
• Organization: Federal Reserve Bank of Atlanta
• References: <8p9j95\$1fo@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Using GenerateConditions -> False elminates the conditions in the
output, even if it doesn't return a completely simplified result:

Integrate[x/Sqrt[x^2 + zp^2]^3, {zp, z, Infinity},
GenerateConditions -> False, Assumptions -> {x > 0, z > 0}]

produces

(1 - (x*z*Sqrt[1 + z^2/x^2])/(x^2 + z^2))/x

-- Mark

Mark Fisher
Research Department
Federal Reserve Bank of Atlanta
Atlanta, GA 30303
404-521-8757 (voice)
404-521-8810 (fax)
mark.fisher at atl.frb.org

personal web page: www.markfisher.net

Jos R Bergervoet wrote:
>
> With the following input:
>
>     Integrate[ x/Sqrt[x^2+zp^2]^3, {zp,z,Infinity},
>       Assumptions -> {x>0, z>0} ]
>
> I get:
>
>                   2    2             2
>     Out[1]= x If[x  + z  >= 0 || Im[x ] != 0,   ....
>
> Why does this if statement appear in the output? Why is Mathematica
> apparently ignoring my directive that x and z are positive?
>
> The same happens with Assumptions -> {x \[Element] Reals,
> z \[Element] Reals}  and with combinations of these two versions.
>
> I would like to have the plain answer (without ifs and whens) to
> use it in further computations. How can it be obtained? (If
> just the lines of input to be typed. I'm not very fond of GUI's ;-)
>
> Jos
>
> --
>   Dr. Jozef R. Bergervoet                      Electromagnetism and EMC
>   Philips Research Laboratories,             Eindhoven, The Netherlands
>   Building WS01                                     FAX: +31-40-2742224
>   E-mail: bergervo at natlab.research.philips.com    Phone: +31-40-2742403

```

• Prev by Date: Re: How to keep things real?
• Next by Date: Evaluate a string
• Previous by thread: Re: Assumptions ignored?
• Next by thread: Hidden parts of a curve as dashed