Re: Question about Integrate and If

*To*: mathgroup at smc.vnet.net*Subject*: [mg46649] Re: Question about Integrate and If*From*: phbrf at t-online.de (Peter Breitfeld)*Date*: Thu, 26 Feb 2004 17:53:56 -0500 (EST)*References*: <c1iqub$69a$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Antonio González <SPAMgonferNO at esi.us.es> wrote: > Setting the trivial integral > > Integrate[1/x,{x,a,2a}] [*snip*] > > Integrate[1/x, {x, a, 2*a}, Assumptions -> a != 0] > > the result is > > If[Im[a] != 0 || Re[a] != 0, Log[2], Integrate[x^(-1), {x, a, 2*a}, > Assumptions -> a != 0 && Im[a] == 0 && Re[a] == 0]] > > that is even worse, as if I assume that a!=0, it is > obvious that Im[a] != 0 || Re[a] != 0 (how could it be > that a != 0 && Im[a] == 0 && Re[a] == 0 ?) > > Can anybody explain this strange behavior? Why does not give > the answer > > If[a!= 0, Log[2],Indeterminate] > > or something like that? > > Antonio That's really strange, but the Assumption->{a<0||a>0} gives the right result. -- Gruß Peter -- ==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-== Peter Breitfeld, Bad Saulgau, Germany -- <http://www.pBreitfeld.de>