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 9,587 of 10,432    |
|    clicliclic@freenet.de to Nasser M. Abbasi    |
|    Re: Computer Algebra Independent Integra    |
|    18 Jul 17 09:23:17    |
      "Nasser M. Abbasi" schrieb:       >       > [...]       >       > One such example in the Hearn test file. #281       >       > Int[Sqrt[9 - 4*Sqrt[2]]*x - Sqrt[2]*Sqrt[1 + 4*x + 2*x^2 + x^4],x]       >       > Your input file says there is no known anti-derivative. So Rubi       > does not solve it, and it got an A using the rule above.       >       > But Maple and Mathematica solved this (result too large to post).       >              This integral is the only such case from the 12 named suites.              Being obviously elliptic, the integral is expressible in terms of the       canonical elliptic integrals. But the necessary factorization of the       radicand into real quadratics is really awkward:              x^4 + 2*x^2 + 4*x + 1 = (x + 1)*(x^3 - x^2 + 3*x + 1) = 1/27*(x + 1)        *(3*x - (6*SQRT(33) - 26)^(1/3) + (6*SQRT(33) + 26)^(1/3) - 1)        *(9*x^2 + 3*((6*SQRT(33) - 26)^(1/3) - (6*SQRT(33) + 26)^(1/3) - 2)*x        + 2*(233 - 39*SQRT(33))^(1/3) + 2*(39*SQRT(33) + 233)^(1/3)        - (6*SQRT(33) - 26)^(1/3) + (6*SQRT(33) + 26)^(1/3) + 9)              as it involves cube roots of square roots.              I therefore suggest to just comment this entry out; in fact, such       appears to be the fate already of another integral from Anthony Hearn's       suite, for which I originally counted 285 distinct entries.              To remind one of the situation, the model antiderivative could perhaps       be set to a placeholder like "awkward".              Martin.              --- 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