Solid of revolution vs. area below 1/x

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SUMMARY

The area under the graph of the function $$\frac{1}{x}$$ from $$[1, \infty)$$ diverges, as demonstrated by the integral $$A = \int_{1}^{\infty} \frac{dx}{x} = \infty$$. In contrast, the volume of the solid of revolution generated by this function in the same interval converges to a finite value, calculated as $$V = \pi\ \int_{1}^{\infty} \frac{dx}{x^{2}} = \pi$$. This phenomenon, often referred to as Gabriel's Horn, illustrates a mathematical paradox first identified by Pappo di Alessandria in the fourth century.

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How come the area below the graph of $$\frac 1x$$ between $$[1, \infty)$$ does not exist, but the solid of revolution below the same graph in that same interval does exist? I do not see the logic.
 
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sweatingbear said:
How come the area below the graph of $$\frac 1x$$ between $$[1, \infty)$$ does not exist, but the solid of revolution below the same graph in that same interval does exist? I do not see the logic.

The calculus demonstrates that the area... $\displaystyle A = \int_{1}^{\infty} \frac{dx}{x} = \infty$ (1)

...and the volume of its the solid of revolution is finite and is... $\displaystyle V= \pi\ \int_{1}^{\infty} \frac{dx}{x^{2}} = \pi$ (2)

It may seem incredible but this 'paradox' was discovered by Pappo di Alessandria in the fourth century after Christ [!]...Kind regards $\chi$ $\sigma$
 
Thank you both for your replies.
 

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