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 ) ] d x {\displaystyle {\begin{aligned}\pi \int _{1}^{2}\left[\left({\frac {1}{x}}\right)\right]dx\end{aligned}}}
![{\displaystyle {\begin{aligned}\pi \int _{1}^{2}\left[\left({\frac {1}{x}}\right)\right]dx\end{aligned}}}](https://en.wikipedia.org/api/rest_v1/media/math/render/svg/83ad0eb0ce8aac1459b8f7e6a8ec1e9f30b32258)