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SolveAPolynomialTimesARationalFunctionOfAnExponential​(AngouriMath.​Entity,​AngouriMath.​Entity.​Variable,​System.​Boolean)

 Method (no overloads)

Summary

A polynomial in x times a rational function of exponentials of x,
by parts against the whole rational function: x tanh(x)^2 is
x ((e^(2x) - 1)/(e^(2x) + 1))^2, whose antiderivative under u = e^(2x) is
x - tanh(x), a polynomial and a rational function of the exponential again,
and what parts leaves is x - tanh(x) itself, a degree lower in x.

Remarks

The general parts rule splits the sum (x + x e^(4x))/(e^(2x) + 1)^2 and takes
each term on its own, and each term's antiderivative in u holds a logarithm
of e^(2x) + 1 -- the two cancel in the sum and neither on its own -- so each
leaves x ln(e^(2x) + 1) behind, a dilogarithm, and twenty-five seconds of
search that found nothing. Here the rational function goes to the exponential
substitution whole, and where its antiderivative keeps a logarithm of an
exponential's sum the integrand is declined at once: x/(e^x + 1) is not
elementary, and this says so in a millisecond.
https://github.com/asc-community/AngouriMath/issues/718

























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