Integral by Parts: Solving 2 Integrals Involving Arctg(x) & Sqrt(1-x^2)

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Discussion Overview

The discussion revolves around the integral of arctg(x) divided by the square root of (1-x^2). Participants explore various methods for solving this integral, including substitution and series expansion, while expressing concerns about the appropriateness of certain techniques given the audience's background.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant suggests using the substitution u = arctg(x) and expresses uncertainty about its effectiveness.
  • Another participant notes that Wolfram Alpha could not find an antiderivative, casting doubt on the existence of one.
  • A participant proposes using the MacLaurin series expansion for arctg(x) to integrate term by term, presenting a specific expansion.
  • Another participant reiterates the series expansion approach but emphasizes the need for traditional methods due to the audience's lack of familiarity with series.
  • A later reply comments on the challenge of solving integrals without having been taught the necessary techniques, indicating frustration with the educational context.

Areas of Agreement / Disagreement

Participants express differing opinions on the methods to be used for solving the integral, with some advocating for series expansion and others insisting on traditional methods. There is no consensus on the best approach.

Contextual Notes

Some participants highlight the limitations of the audience's knowledge, specifically mentioning that they have not studied series yet, which affects the applicability of certain proposed methods.

Who May Find This Useful

Students and educators interested in integral calculus, particularly those exploring different methods of integration and the challenges of teaching complex topics without prior foundational knowledge.

leprofece
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integral of arctg(x)/sqrt(1-x^2)

maybe u = arctg x du = 1 /1+x^2
but x = tg u
maybe this is the way isn't it?
 
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Wolfram couldn't find an antiderivative so I doubt there is one...
 
leprofece said:
integral of arctg(x)/sqrt(1-x^2)

maybe u = arctg x du = 1 /1+x^2
but x = tg u
maybe this is the way isn't it?

A possible approach is to use the MacLaurin expansion...

$\displaystyle \frac{\tan^{-1} x}{\sqrt{1-x^{2}}} = x + \frac{1}{6}\ x^{3} + \frac{49}{120}\ x^{5} + \frac{81}{560}\ x^{7} + \mathcal{O}\ (x^{9})\ (1)$

... and to integrate term by term...

Kind regards

$\chi$ $\sigma$
 
chisigma said:
A possible approach is to use the MacLaurin expansion...

$\displaystyle \frac{\tan^{-1} x}{\sqrt{1-x^{2}}} = x + \frac{1}{6}\ x^{3} + \frac{49}{120}\ x^{5} + \frac{81}{560}\ x^{7} + \mathcal{O}\ (x^{9})\ (1)$

... and to integrate term by term...

Kind regards $\chi$ $\sigma$

Thank for your answer but you must solve it by normal or traditional methods students have not studied series yet
Could anybody do that way??
 
leprofece said:
Thank for your answer but you must solve it by normal or traditional methods students have not studied series yet
Could anybody do that way??

Hey! :D

As with your other recent thread - for $$\int \sqrt{x}e^x\, dx$$ - it sounds like your teacher is asking you to do stuff without him or her teaching you the things necessary to solve the problem... (Headbang)
 

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