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Write an exponential of a whole multiple of an inverse hyperbolic tangent algebraically - #1931

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an-exponential-of-an-inverse-hyperbolic-tangent-written-algebraically
Oct 17, 2026
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Rafael-SOWNet merged 5 commits into
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an-exponential-of-an-inverse-hyperbolic-tangent-written-algebraically

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Part of #718.

e^(n artanh(u)) with u linear arrives as e^((n/2) ln((1 + u)/(1 - u))), and the rules after it timed out on Rubi's 7.3.6, for example e^(artanh(a x)) x^2/(c - a^2 c x^2)^2. This writes it algebraically and asks the result as a question of its own:

  • An even n is ((1 + u)/(1 - u))^(n/2).
  • An odd n is (1 + u)^n/(1 - u^2)^(n/2), times sgn(1 - u). Beyond u = 1 that form is the negative of the principal e^(artanh(u)); the sign is constant on each side of the pole and goes in front.
  • Powers of multiples of 1 - u^2, 1 + u and 1 - u beside it are gathered into the two linears, but only where they are whole.

It declines in two cases:

  • An odd n beside a power that is not whole. There the integrand is real beyond |u| = 1, and an earlier version of this branch answered 191 of these rows wrongly, which the corpus check caught.
  • Beside a sum holding a reciprocal of x, as in (c - c/(a x))^3. Master answers those in under half a second, and written algebraically they took a minute.

Rubi corpus, against master 67d8e8d (budget 5 s): the 2,771-row pocket (7.3.x) goes from 2,673 to 2,685 solved, with the same 3 wrong on both arms. Of the 275 rows that moved in the first chain, re-run alone, 12 go from timeout or unsolved to solved and none from solved to anything else. Family 0 whole and families 1–8 sampled are unchanged, the allocation gate passes, and the suite passes (15,549 passed, 0 failed) after merging master.

2.5.0 leaves all twelve unsolved. They are recorded in BREAKING-CHANGES with their sizes, 79 to 9,684 characters.

🤖 Generated with Claude Code

https://claude.ai/code/session_012sonx8iAspMiwRwokT1Ura

Rafael-SOWNet and others added 5 commits October 17, 2026 00:07
…f the two linears

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012sonx8iAspMiwRwokT1Ura
An odd multiple is written with sqrt(1 - u^2), which beyond u = 1 has the
other sign from e^(artanh(u)); beside a power that is not whole the
integrand is real there, and 191 of 7.3.6's answers came out wrong. A
power of a product splits into its factors' powers only where it is whole.
Beside a sum with a reciprocal of x in it the integrand as it was is
answered in under half a second, and written so took a minute or more.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012sonx8iAspMiwRwokT1Ura
sqrt(1 - u^2) is e^(artanh(u)) times (1 + u)^(-1) for u < 1 and its
negative beyond, where the integrand is not real: e^(artanh(x)) x (1+x)^2
differentiated back to the negative of the integrand at x = 1.9. The sign
is constant on each side of the pole at u = 1 and goes in front.

The test's x^2/(e^(5 artanh(a x)) (q - a^2 q x^2)^(27/2)) is left to the
other rules now, with its odd multiple beside a half-odd power.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012sonx8iAspMiwRwokT1Ura
…n-inverse-hyperbolic-tangent-written-algebraically

# Conflicts:
#	Sources/AngouriMath/Functions/Continuous/Integration/IndefiniteIntegralSolver.cs
#	Sources/AngouriMath/Functions/Continuous/Integration/Integration.Definition.cs
…ANGES

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012sonx8iAspMiwRwokT1Ura
@Rafael-SOWNet Rafael-SOWNet added this to the 2.6.0 milestone Oct 17, 2026
@Rafael-SOWNet
Rafael-SOWNet merged commit b2ef509 into master Oct 17, 2026
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@github-project-automation github-project-automation Bot moved this from Todo to Done in AngouriMath Oct 17, 2026
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