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

 Method (no overloads)

Summary

A symbolic power of sinh(y) beside an odd whole power of cosh(y), under
u = sinh(y), where cosh(y)^(2j + 1) dy is (1 + u^2)^j du; and a
symbolic power of cosh(y) beside an odd power of sinh(y), under
u = cosh(y), with (u^2 - 1)^j. cosh(a + b x)^3 sinh(a + b x)^n is
(1 + u^2) u^n/b. A symbolic power of sech(y) or csch(y) the same way
under u = sech(y) or u = csch(y), with tanh(y) and coth(y) beside it read as quotients: sech(a + b x)^n tanh(a + b x)^3 is
sinh^3 cosh^(-3) sech^n, which is -(1 - u^2) u^(n - 1)/b.
https://github.com/asc-community/AngouriMath/issues/233

Remarks

Rubi's four in 6.7.1 were past the budget:
SolveByBiochesOddHyperbolicSubstitution(AngouriMath.Entity,AngouriMath.Entity.Variable,System.Boolean) reads whole and rational powers, and
a symbolic one is neither. Exact: d/dx F(sinh(y)) = y' cosh(y) F'(sinh(y)) wherever
F is differentiable, whatever the power, and (1 + sinh(y)^2)^j = cosh(y)^(2j) for a whole j. Odd powers from three: the first is the derivative of a power beside
it, which the rules for that answer. So were its sech(a + b x)^n tanh(a + b x)^3 and
coth(a + b x)^3 csch(a + b x)^n. The reciprocal is the variable, not its reciprocal
to the power negated: csch(y)^n is e^(2 pi i n) sinh(y)^(-n) where the sine is
negative, and u^n under u = csch(y) is csch(y)^n everywhere.

























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