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|    sci.math.symbolic    |    Symbolic algebra discussion    |    10,432 messages    |
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|    Message 8,475 of 10,432    |
|    clicliclic@freenet.de to Albert Rich    |
|    Re: The A. F. Timofeev symbolic integrat    |
|    14 Nov 13 21:11:17    |
      Albert Rich schrieb:       >       > On Wednesday, November 13, 2013 1:56:55 AM UTC-10, clicl...@freenet.de wrote:       >       > > The hypergeometric series here (and in Example 3) terminate for a       > > non-negative integer exponent n, while the series for your evaluation of       > > Examples 6a,b terminate (after applying Euler's transformation) for a       > > negative integer exponent n. The latter type of representation is       > > somewhat more compact; a disadvantage is that the antiderivative 6a for       > > positive a,m,x ends up on the branch cut of the hypergeometric function.       > > I therefore propose to normalize to the former type:       >       > For the integral of (1+x)^n/x, Rubi currently returns       >       > -(1+x)^(1+n) * 2F1(1,1+n,2+n,1+x) / (1+n)       >       > In light of your comments above, would it be better to return       >       > (1+x)^n * 2F1(-n,-n,1-n,-1/x) / (n*(1+1/x)^n) ?       >              I think so. For positive x and non-integer n you are no longer sitting       right on the edge of a cliff then - the thought alone makes me dizzy. An       equivalent (by Euler's transformation) but simpler antiderivative is:               (1+x)^(1+n) * 2F1(1,1,1-n,-1/x) / (n*x)              Note that the singularity at x=0 is already present in the integrand.       And Pfaff's transformation of these two puts one on the brink of the       chasm when x is negative and small:               (1+x)^n * 2F1(-n,1,1-n,1/(1+x)) / n              Martin.              PS: I have seen your "piecewise constants" called "differential       constants" by WRI's Daniel Lichtblau, but the former term is much much       more popular according to Google.              --- SoupGate-Win32 v1.05        * Origin: you cannot sedate... all the things you hate (1:229/2)    |
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