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