How do you find the volume of the solid generated by revolving the region bounded by the graphs #y=e^-x, y=0, x=0, x=1#, about the x axis?
At any distance x, they coordinate happens to be the radius of the revolved element
Circular area generated by revolving around x axis is
volume of the elementary solid of thickness dx is
The lower limit is given to be x=0
The upper limit is given to be x=1
Integrating between x=0 and x=1