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Revision difference : Torricelli's trumpet
Version 8 Version 7
\emph{Torricelli's trumpet} is a fictional infinitely long solid of revolution formed when the closed domain \emph{Torricelli's trumpet} is a fictional infinitely long solid of revolution formed when the closed domain
$$A := \{(x,\,y)\in\mathbb{R}^2\,\vdots\;\; x \ge 1,\; 0 \le y \le \frac{1}{x}\}$$ $$A := \{(x,\,y)\in\mathbb{R}^2\,\vdots\;\; x \ge 1,\; 0 \le y \le \frac{1}{x}\}$$
rotates about the $x$-axis. It has a finite volume, $\pi$ volume \PMlinkescapetext{units}, but the area of its surface is infinite; in fact even the area of $A$ is infinite, i.e., the improper integral $\displaystyle\int_1^\infty\frac{1}{x}\,dx$ is not convergent. rotates about the $x$-axis. It has a finite volume, $\pi$ volume \PMlinkescapetext{units}, but the area of its surface is infinite; in fact even the area of $A$ is infinite, i.e., the improper integral $\displaystyle\int_1^\infty\frac{1}{x}\,dx$ is not convergent.
Torricelli's trumpet is surprising since the the solid can be filled by a finite amount Torricelli's trumpet is paradoxical since the the solid can be filled by a finite amount
of paint, but this paint can never suffice for painting the surface of the body, no matter of paint, but this paint can never suffice for painting the surface of the body, no matter
how \PMlinkescapetext{thin} a coat of paint is used! how \PMlinkescapetext{thin} a coat of paint is used!
\PMlinkescapeword{even} \PMlinkescapeword{even}