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we need more integral solvers #233

Description

@MomoDeve

There are a lot of stuff to do, but to begin with, I will put some unsolvable by AM integrals here:

  • cos(x^2)*x variable substitution method, WolframAlpha
  • sin(x)*e^x integrating by parts and solving integral equation, WolframAlpha
  • 1/(a^2 + x^2) standard integral for arctan, WolframAlpha
  • x^2 / (x^4 + 1) partial fractioning WolframAlpha
  • sqrt(tan(x)) very painful, requires different solvers, WolframAlpha

I do not mention special integrals here, like e^(x^2) or 1/ln(x)

Activity

  1. linked a pull request that will close this issueIndefinite integration #229on Oct 9, 2020
  2. added this to the 1.2.3 milestone on Oct 16, 2020
  3. added
    AcceptedFor proposals, which were approved and will be implemented
    on Mar 24, 2021
  4. Rafael-SOWNet commented on Aug 16, 2026

    @Rafael-SOWNet
    Member

    Three of the five are done. Measured on master at a45a7256, each verified by differentiating the answer back rather than by eye.

    integrand today check
    cos(x^2)*x sin(x^2) / 2 + C d/dx matches
    sin(x)*e^x e^x * (sin(x) - cos(x)) / 2 + C d/dx matches
    1/(a^2 + x^2) a piecewise on the sign of a^2, with arctan(x / sqrt(a^2)) / sqrt(a^2) + C on the positive branch correct — see below
    x^2 / (x^4 + 1) unevaluated —
    sqrt(tan(x)) unevaluated —

    So the substitution case, the by-parts-and-solve-the-equation case, and the arctan standard integral are all answered. The two left are the two the body itself flags as hardest — partial fractioning over an irreducible quartic, and sqrt(tan(x)), which it calls "very painful, requires different solvers". Both are also the two casbench reports unsolved, so this agrees with the corpus.

    On the arctan one, a correction to my own first reading. Differentiating it back and simplifying does not reduce to zero, and I nearly reported that as a wrong answer. It is not — the piecewise carries branch conditions that block symbolic cancellation. Checked numerically instead:

    a x d/dx of the antiderivative integrand difference
    2 1 1/5 1/5 0
    3 -2 1/13 1/13 0
    1 0.5 4/5 4/5 0
    5 4 1/41 1/41 0

    Worth recording because it will catch the next person too: an antiderivative that comes back as a Piecewise cannot be verified by simplifying d/dx F - f to zero, and a harness that does so will report a false defect.

    Suggest ticking the three and leaving this open for the remaining two.

  5. removed this from the 1.6 milestone on Sep 18, 2026
  6. 7 remaining items

  7. modified the milestones: 2.6.0, 2.8 on Sep 30, 2026
  8. modified the milestones: 2.8, 2.6.0 on Sep 30, 2026
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