Impossible Integration involving cosx/sqrt(a-bcosx)

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SUMMARY

The integral \(\int \frac{\cos x}{\sqrt{a - b \cos x}}dx\) presents significant challenges for integration using standard techniques such as integration by parts, half-angle formulas, and substitutions. Users have reported that tools like Wolfram Alpha and Mathematica yield results consistent with those found in Gradshteyn and Ryzhik's integral tables, indicating that this integral may not have a solution expressible in elementary functions. The discussion highlights the necessity of recognizing when integrals require special functions for resolution, emphasizing the limitations of traditional methods in certain cases.

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  • Understanding of integral calculus and techniques such as integration by parts and substitution.
  • Familiarity with special functions like the error function (erf) and elliptic integrals.
  • Experience using computational tools like Wolfram Alpha and Mathematica for integral evaluation.
  • Knowledge of integral tables, specifically Gradshteyn and Ryzhik.
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  • Research the properties and applications of elliptic integrals.
  • Learn how to use Wolfram Alpha for complex integral evaluations.
  • Explore advanced integration techniques beyond standard calculus methods.
  • Study the error function (erf) and its role in solving integrals that cannot be expressed in elementary terms.
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Mathematicians, calculus students, and anyone involved in advanced integration techniques or seeking to understand the limitations of traditional methods in solving complex integrals.

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Ok, I have encountered this one a few hours ago:
\int \frac{cos x}{\sqrt{a - b cos x}}dx
I have tried all techniques I know, integration by part, half-angle formula, substitution, trigo approach, and so on, but it seems, I could not integrate this one. I am no noob in integration, but this one is a bit difficult. How do I integrate it?
 
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Wolfram Alpha? Integral table?
 
I suspected that. After I learned that a lot of integrals cannot be solved without essentially defining a new function (like erf and the ellipticals), I got in the habit after spinning my wheels a bit with the standard techniques of looking them up in G&R to see if they were do-able.

When MMa came along, it was faster than looking in G&R. WA is even more convenient.
 
Yes of course, it is really convenient to look into table of integrals, but it is just impossible to do on exams. I hope we could have a technique to solve it.
 

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