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Here Are Two Math Mistakes And One English Mistake

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Posted by Paul R. Martin on June 1, 2003 00:22:25 UTC

Hi Yanniru,

Your integrand for the volume, pi/x, is incorrect.

Your integrand for the surface area, 2pi/x^2, is also incorrect.

To calculate volume, the general expression for the integrand of a figure of revolution is pi r^2 dx. Where r is the radius. You need to express that radius as the function y=1/x^3 for Nelson's problem.

To calculate the surface area, the general expression for the integrand is 2 pi r ds, where ds is sqrt ( 1 + dy/dx)^2 ) dx. Again, you need to express r as the function y=1/x^3 in order to solve Nelson's problem.

Moving on from math to English, "scathing" might apply but "derision" does not. It is not in my nature to deride people and I did not deride you. I simply pointed out pertinent facts.

Warm regards,


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