Power series of inverse trig functions

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Discussion Overview

The discussion focuses on finding the power series for inverse trigonometric functions, particularly arcsin. Participants explore different methods for deriving these series, including manipulation of existing power series and integration techniques.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the power series for arcsin can be derived by manipulating the power series for sin, expressing uncertainty about this approach.
  • Another participant argues against the feasibility of this method, citing complications even with simpler functions like y = x^(2n).
  • A different viewpoint suggests that it is possible to find the power series through "reversion" of a series, although this method becomes increasingly complex.
  • Another participant proposes starting with the binomial series for (1-x^2)^{-1/2} and integrating term-by-term as a more effective method for deriving the series for arcsin.
  • One participant introduces the idea of identifying the inverse trig function as a hypergeometric function and manipulating its series expansion, referencing resources on hypergeometric functions for necessary formulas.

Areas of Agreement / Disagreement

Participants express differing opinions on the methods for deriving power series for inverse trigonometric functions, indicating that multiple competing views remain without a consensus on the best approach.

Contextual Notes

Some methods proposed depend on specific mathematical techniques, such as series reversion and integration of binomial series, which may have limitations or require further assumptions not fully explored in the discussion.

zeebo17
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How do you find the power series for inverse trig functions? Can I find the power series for arcsin by manipulating the power series for sin?

Thanks!
 
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I don't think so.
Even for the simplest of functions you already run into trouble, consider for example y = x2n (for n = 1, 2, ...). The power series for x1/(2n) is already non-trivial.
 
You can, it is called "reversion" of a series. But the formulas get more and more complicated as you proceed.

For arcsin, a better way to find the series is to start with the binomial series for (1-x^2)^{-1/2} and integrate term-by-term.
 
Identify the inverse trig function as a hypergeometric function, and manipulate the series expansion of the hypergeometric function. Any book on hypergeometric functions will give the necessary formulae.
 

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