Proper way to graph xy = 1 for a cylindrical shell problem

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Homework Help Overview

The discussion revolves around the proper method to graph the equation xy = 1 in the context of a cylindrical shell problem, particularly focusing on the integration process when rotating around the x-axis.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the choice between using x = 1/y and y = 1/x for integration, questioning how these representations affect the integration process and the variables involved.

Discussion Status

There is an ongoing exploration of the necessity for the integrand to match the variable of integration. Some participants assert that the integrand must be in terms of y when integrating with respect to y, while others express uncertainty about the implications of using different variable representations.

Contextual Notes

Participants are considering the implications of integrating with respect to y versus x, and the potential confusion arising from the different forms of the equation. There is an emphasis on ensuring clarity in variable usage during integration.

Eddie10
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Homework Statement


Proper way to graph xy = 1 for a Cylindrical Shell problems.

Homework Equations



V = ∫^b_a 2πy f(y) dy

The Attempt at a Solution


I am rotating around the x-axis, so I am integrating with respect to y, but should I choose x = 1/y, or y = 1/x to solve my problem?

How are these two functions different? x = 1/y and y = 1/x different?
 
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They aren't different. Why do you think they are?
 
vela said:
They aren't different. Why do you think they are?
Well, if I am integrating with all y variables, shouldn't it make sense to use x = 1/y, instead of y = 1/x, so the variables match? For example, v = 2pi (Integrand Sign) f(y) dy.

Or, in this case, does the variables used not affect the answer once integration is applied?
 
Yes, of course. You need the integrand to be in terms of ##y## if you're integrating with respect to ##y##. Isn't this always the case? I guess I'm not sure why you'd think you could use 1/x in this case.
 
vela said:
Yes, of course. You need the integrand to be in terms of ##y## if you're integrating with respect to ##y##. Isn't this always the case? I guess I'm not sure why you'd think you could use 1/x in this case.

Yeah, I was double checking to make sure I couldn't use 1/x in this case, since I am integrating everything for "dy" instead of "dx".

Thanks.
 

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