Re: A couple of curious outputs from Integrate[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg13655] Re: A couple of curious outputs from Integrate[]*From*: Jean-Michel Collard <jcollard at iissun4.unil.ch>*Date*: Sat, 08 Aug 1998 14:14:31 +0300*Organization*: Universite de Lausanne*References*: <6qbrkd$a8b@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

James Lawry wrote: > > Here are a couple of Integrate[] commands that produce very odd results > in Mathematica 3.0 for Sparc. > > 1: Try > Integrate[Exp[-x Log[x]] Sin[x], {x, 0, Infinity}] > > This returns a value that contains x. This is silly, since it is a > definite integral and x is a dummy variable of integration. Version 2.2 > returned this integral unevaluated. > > 2: Make sure that there's nothing unsaved in your Mathematica session, > and try > > Integrate[Log[x]^2 Exp[-x], {x, 0, Infinity}] > > This produces more spectacular results in the Sparc notebook version of > Mathematica than in the text version, which just grumbles loudly for > several minutes before producing the answer. Version 2.2 of Mathematica > produced the answer in a few seconds. > > James Lawry. In[1]:= Integrate[Log[x]^2 Exp[-x], {x, 0, Infinity}] 2 2 Pi Out[1]= EulerGamma + --- 6 In[2]:= Integrate[Exp[-x Log[x]] Sin[x], {x, 0, Infinity}] Pi x Out[2]= Cos[----] Gamma[1 - x] Perfect. JMC