home bbs files messages ]

Forums before death by AOL, social media and spammers... "We can't have nice things"

   sci.math.symbolic      Symbolic algebra discussion      10,432 messages   

[   << oldest   |   < older   |   list   |   newer >   |   newest >>   ]

   Message 9,646 of 10,432   
   Albert Rich to Albert Rich   
   Re: fyi, new build of CAS integration te   
   04 Oct 17 04:56:07   
   
   From: Albert_Rich@msn.com   
      
   On Tuesday, October 3, 2017 at 5:58:21 PM UTC-10, Albert Rich wrote:   
      
   > However, there may still remain a problem.  For the pseudo-elliptic   
   integrand 1/((2-x^2)*(x^2-1)^(1/4)), Rubi returns   
   >    
   >     ArcTan[x/(Sqrt[2]*(x^2-1)^(1/4))]/(2*Sqrt[2]) +    
   >     ArcTanh[x/(Sqrt[2]*(x^2-1)^(1/4))]/(2*Sqrt[2])   
   >    
   > which is never real on the real line, although the integrand is when x^2>1.    
   This is analogous to the way log(x) is not real when x<0, although 1/x is real   
   on the entire real line.  So is the above antiderivative for 1/(   
   2-x^2)*(x^2-1)^(1/4)) optimal    
   in terms of reality?   
   >    
   > Albert   
      
   Converting the above arctanh term to a log you get    
      
       ArcTan[x/(Sqrt[2]*(x^2-1)^(1/4))] / (2*Sqrt[2]) +    
       Log[(Sqrt[2]*x+2*(x^2-1)^(1/4))/   
           (Sqrt[2]*x-2*(x^2-1)^(1/4))] / (4*Sqrt[2])   
      
   for the antiderivative of 1/((2-x^2)*(x^2-1)^(1/4)), which magically is real   
   in all the right places and hence optimal.   
      
   Albert   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

[   << oldest   |   < older   |   list   |   newer >   |   newest >>   ]


(c) 1994,  bbs@darkrealms.ca