y = 1 x , x = 1 , x = 2 , y = 0 ; about the x-axis {\displaystyle y={\frac {1}{x}},x=1,x=2,y=0;{\text{about the x-axis}}}
π ∫ 1 2 [ ( 1 x ) 2 ] d x = π ∫ 1 2 [ ( 1 x 2 ) ] d x {\displaystyle {\begin{aligned}\pi \int _{1}^{2}\left[\left({\frac {1}{x}}\right)^{2}\right]dx&=\pi \int _{1}^{2}\left[\left({\frac {1}{x^{2}}}\right)\right]dx\end{aligned}}}
![{\displaystyle {\begin{aligned}\pi \int _{1}^{2}\left[\left({\frac {1}{x}}\right)^{2}\right]dx&=\pi \int _{1}^{2}\left[\left({\frac {1}{x^{2}}}\right)\right]dx\end{aligned}}}](https://en.wikipedia.org/api/rest_v1/media/math/render/svg/0709bd6c54ef2b18769b0c45158e73712934f9cd)