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|    sci.math.symbolic    |    Symbolic algebra discussion    |    10,432 messages    |
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|    Message 8,923 of 10,432    |
|    clicliclic@freenet.de to Basti05b@aol.com    |
|    Re: Equations of Physics and Engineering    |
|    13 Dec 15 14:11:55    |
      Basti05b@aol.com schrieb:       >       > [...] In Volume 1 of my book, we use Riccati theorems to handle       > classical equations of physics and engineering.       >       > [...] Applications are ranging from solving integrations to       > differential equations. For example, as noted in DNA of mathematics       > book, the following function:       >       > S1: (t+2)/(t*sqrt((t+1)*(2*t^2+b*(t+1))));       >       > Where b is a non-zero real number, has integration of all rational       > functions.       > However Maple, and Mathematica, expresses them with Elliptic       > functions.       >              A response should be in order here. Straightforward testing shows that       your integrand S1 is Goursat-pseudoelliptic and its antiderivative in       terms of elementary transcendental functions can be obtained by       substituting x^2 = (t + 1)/(2*t^2 + b*t + b). The result is simply:              - 1/SQRT(b)        *ATANH((t^2 + b*t + b)/(SQRT(b)*SQRT((t + 1)*(2*t^2 + b*t + b))))              For example, FriCAS manages to evaluate this in elementary terms. But       the DNA of this class of integrands has been sequenced in Goursat's 1887       paper "Note sur quelques intégrales pseudo-elliptiques" already.              On the other hand, Fricas returns "Error detected: impossible" for the       cube-root pseudoelliptic 1/(x*((x - 1)*(x^2 - 2*q*x + q))^(1/3)) which,       however, may well be beyond all current integrators. Still, as the Risch       approach to general cube-root algebraics could not be made to work       during the last 25 years, one may doubt that it is practical at all.              Martin.              --- SoupGate-Win32 v1.05        * Origin: you cannot sedate... all the things you hate (1:229/2)    |
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