Shell's Method: Solids of Rotation, Torus

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SUMMARY

The discussion focuses on calculating the volume of a torus using Shell's method, specifically the integral 4π ∫ from -1 to 1 of ((R-x) √(r² - x²)) dx. Participants express difficulty in integrating this expression using conventional methods and suggest alternative approaches, including trigonometric substitution (x = r cos(t) or x = r sin(t)) and integration by parts. The importance of adjusting the limits of integration and the differential dx during substitution is emphasized as a critical step in solving the problem.

PREREQUISITES
  • Understanding of Shell's method for volume calculation
  • Familiarity with trigonometric substitution techniques
  • Knowledge of integration by parts
  • Basic concepts of definite integrals and their limits
NEXT STEPS
  • Study the application of Shell's method in different geometric contexts
  • Learn about trigonometric substitution in integral calculus
  • Practice integration by parts with various functions
  • Explore the properties of definite integrals and their transformations
USEFUL FOR

Students and educators in calculus, particularly those focusing on volume calculations and integration techniques. This discussion is beneficial for anyone looking to deepen their understanding of advanced integration methods in mathematical analysis.

teken894
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Homework Statement



Volume of Torus: using Shell's mehod

4\pi \int^{1}_{-1}((R-x) \sqrt{r^2 - x^2})dx

Homework Equations


The Attempt at a Solution



I don't know how to integrate this at all. I cannot use any conventional methods...or I can't think of a way... i.e. use isolate a function as u and try to integrate wrt du

Is the only way to distribute the equation first?
 
Last edited:
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try trig substitution, e.g. x=rcost or x=rsint. i did not complete it myself but that should work. after that you may need to do integration by parts. don't forget dx changes too, as does -1 and 1.
 
Last edited:

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