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
Economic Advisor
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
> possible, do not give answers about menus and mouseclicks, but
> just the lines of input to be typed. I'm not very fond of GUI's ;-)
>
> Thanks in advance,
> 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