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|    sci.math.symbolic    |    Symbolic algebra discussion    |    10,432 messages    |
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|    Message 9,361 of 10,432    |
|    clicliclic@freenet.de to Richard Fateman    |
|    Re: The Risch algorithm    |
|    15 Apr 17 18:41:30    |
      Richard Fateman schrieb:       >       > [...]       >       > It seems to me that the integrand log(x)*log(x^2), considered       > algebraically, is 2*log(x)^2. Are you trying to say something       > subtle about it by stating it in that form?              With this identification of distinct integrands you are pointing to the       root of the problem. The systems I know insist that LN(x)*LN(x^2) /=       2*LN(x)^2 for any x < 0, in violation of your identification. For x =       -1, Mathematica and Derive thus simplify the left-hand side to zero and       the right-hand side to -2*pi^2. I expect Maxima to do so too.              Maxima and Mathematica both claim to employ Risch techniques for       transcendental integrands. Judging from the respective antiderivatives,       Maxima seems to rely on the problematic identification like FriCAS does,       whereas Mathematica manages without.              Instances where DIF(INT(f(x), x), x) /= f(x) must be considered       manifestations of a bug as both sides are usually understood to be       mathematically equal. Like FriCAS, you are therefore having a       consistency problem if this equality is violated by your system in the       case of f(x) = LN(x)*LN(x^2).              I am not surprised that Maxima too isn't perfect :). Sympy would be       another candidate to check.              Martin.              --- SoupGate-Win32 v1.05        * Origin: you cannot sedate... all the things you hate (1:229/2)    |
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