AngouriMath

Navigation

← Back to list of members

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

 Method (no overloads)

Summary

A whole power m <= -2 of a linear beside a power that is not whole of another,
times a polynomial: 1/((a + b x)^4 sqrt(c + d x)),
(A + B x + C x^2)/((a + b x)^3 (c + d x)^(3/2)). The polynomial is written in powers
of the first linear, and each negative power is raised to -1 by the recurrence
int L1^m L2^n = L1^(m + 1) L2^(n + 1)/((m + 1) D) - (m + n + 2) d/((m + 1) D) int L1^(m + 1) L2^n,
L1 = a + b x, L2 = c + d x, D = b c - a d; what is left are the
questions int L2^n/L1 and int L1^k L2^n for k >= 0, which the
integrator answers in a step.

Remarks

The recurrence is the derivative of L1^(m + 1) L2^(n + 1), which is
L1^m L2^n ((m + 1) D + (m + n + 2) d L1), read back. Under v = sqrt(c + d x) the same integrand is a rational function over a power of a quadratic with symbols in
it, and the reduction of that took four seconds at the square and twenty at the fourth
power; and the partial fractions of a rational function beside a root are terms of
exactly this shape, so it is their cost too.
A closed reduction to smaller questions of another shape, so at any depth.
https://github.com/asc-community/AngouriMath/issues/718

























Angouri © 2019-2023 · Project's repo · Site's repo · Octicons · Transparency · 4862 pages online