Solids Formed From Certain Cross Sections
This applet illustrates solids formed by "prism stacking".  
Various possible cross-sections are shown to the left.  Select any one you'd like.  
f = greater (upper) function
g = lesser (lower) function
n = number of equal intervals into which the interval [a, b] is divided.  
Note:  Cross sections are drawn parallel to the y-axis.  
Enjoy!