Volumesby the Methodof Disks(revolutionaboutthe -axis)Becausethe shapesof the cross-sectionsare circularor look like the shapesof disks,the applicationof this
methodis commonlyknownas the methodof disks.
Example 2
Calculatethe volumeof the solidthat is obtainedwhenthe regionunderthe curve is revolvedabout
the -axisover the interval
Solution:
As Figures9a and 9b show, the volumeis