Partial Fractions: Simplifying Square Root Fractions

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Discussion Overview

The discussion centers on the simplification of fractions involving square roots, specifically exploring whether there is a general method for converting such expressions into simpler forms, akin to the partial fraction decomposition used for rational functions. The scope includes theoretical considerations and mathematical reasoning.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant inquires about a general method for simplifying fractions with square roots, comparing it to the method for rational fractions.
  • Another participant suggests that substituting \( x = \cos\theta \) might help in certain cases, as it transforms the square root expression.
  • A different participant argues that the expression cannot be represented as a sum of partial fractions because it yields irrational values for some rational inputs, which contradicts the nature of rational functions.
  • This participant also mentions the possibility of finding a Taylor series for the expression, noting that it would be convergent within certain intervals where the function is defined.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of simplifying square root fractions into partial fractions, with some suggesting alternative methods while others assert that such simplification is not feasible.

Contextual Notes

The discussion highlights limitations regarding the convergence of Taylor series and the conditions under which the original function is defined and differentiable.

phymatter
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is there a general way of converting fractions involving square root like (1+x)/(1-x)1/2 to simpler fractions , like we have a method of converting rational fractions into sum of partial fractions ?
 
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hi phymatter! :smile:

not that i know of, except that sometimes it may help to substitute x = cosθ, so that √(1 - x) = (√2)sin(θ/2) :wink:
 
phymatter said:
is there a general way of converting fractions involving square root like (1+x)/(1-x)1/2 to simpler fractions , like we have a method of converting rational fractions into sum of partial fractions ?

You wouldn't get this expression equal to a sum of partial fractions, since a sum of partial fraction is a rational function and would therefore for rational number input yield rational values. Your function involving a square root will yield irrational values for some rational numbers, which clearly is contradictory. Allowing infinite sums you could however find the Taylor series for your expression. http://en.wikipedia.org/wiki/Taylor_series

This will however normally only be convergent for some open interval where your function is infinitely differentiable, but for your function you could find a Taylor series around every point where it is defined (since your particular function is infinitely differentiable whenever it is defined).
 
Thank You , Jarle and tiny-tim for your help :smile: !
 

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