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 = π [ − 1 x ] B i g g | 1 2 {\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\\[2ex]&=\pi \left[-{\frac {1}{x}}\right]Bigg|_{1}^{2}\\[2ex]\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\\[2ex]&=\pi \left[-{\frac {1}{x}}\right]Bigg|_{1}^{2}\\[2ex]\end{aligned}}}](https://en.wikipedia.org/api/rest_v1/media/math/render/svg/265c5148db8fe94ff48afb432a55e9f411c5d8ef)