AngouriMath
SolveAPowerOfAnInverseFunctionOfAQuadraticByTheRecurrence(AngouriMath.Entity,AngouriMath.Entity.Variable)
Method (no overloads)
Summary
A whole power of a + b u , where u is the inverse sine or cosine of
w = c + d x^2 with c^2 = 1 , the inverse hyperbolic cosine of one, or the
inverse hyperbolic sine of one withc^2 = -1 , by the recurrence
integral (a + b u)^n = x (a + b u)^n + 2 e n b H (a + b u)^(n - 1) - 4 e b^2 n (n - 1) integral (a + b u)^(n - 2) ,
withH = 1/(d x u'(w)) , e = 1 for the circular functions and -1 for the
hyperbolic ones. It closes atn = 0 and n = 1 , so nothing is asked below. A
negative power goes throughu : w - c is a constant times g(u/2 + beta)^2 for a sine or a cosine g , so x/g is constant on each side of 0, and the
powers-1 and -2 are sine and cosine integrals of (a + b u)/(2 b) (hyperbolic ones for the hyperbolic cosine and sine), the rest the recurrence run backwards.
Exact on the real domain; off itx/g can change sign across a cut. For the inverse
hyperbolic sineg is cosh(u/2 + c pi/4) : cosh(u/2) + c sinh(u/2) is
sqrt(2) times it, and its square is 1 + c sinh(u) = c d x^2 .
inverse hyperbolic sine of one with
with
hyperbolic ones. It closes at
negative power goes through
powers
Exact on the real domain; off it
hyperbolic sine
Remarks
Each u has u'' = e w u'^3 , and with c^2 = 1 (or -1 ) the radicand of
u' is d x^2 (2 c + d x^2) up to sign, so H u' = 2 and
(x (a + b u)^n + 2 e n b H (a + b u)^(n - 1))' is (a + b u)^n plus a multiple of
(a + b u)^(n - 2) . Rubi's 5.1.5, 5.2.5 and 7.2.5 (a + b acos(1 + d x^2))^4 and the like were declined, and 7.1.5 1/(a + b asinh(i + d x^2))^n , which had no
row in the table below.
https://github.com/asc-community/AngouriMath/issues/718
row in the table below.
https://github.com/asc-community/AngouriMath/issues/718
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