Re: Intelligent handling of Infinity in Limits

*To*: mathgroup at smc.vnet.net*Subject*: [mg7645] Re: [mg7622] Intelligent handling of Infinity in Limits*From*: jpk at max.mpae.gwdg.de*Date*: Tue, 24 Jun 1997 03:36:08 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hi Peter, > i was trying to do Integrate[ r^2 Exp[-a r^2], {r,0,Infty}] but MMA > couldn't simplify a term which clearly was zero. Look tin "The Book" -- every Mma identifyer is a full (!) english word starting with a capital, so You have to type Infinity instead of the TeX abbrevation \infty than all works fine : In[12]:= Integrate[ r^2 Exp[-a r^2], {r,0,Infinity}]//InputForm Out[12]//InputForm= If[Re[a] > 0, Sqrt[Pi]/(4*a^(3/2)), Integrate[r^2/E^(a*r^2), {r, 0, Infinity}]] > > next i tried integrating over {r,0,r} and then took the limit as r->Infty. > Again Infinity ! Hope that helps Jens