15.4: Disk Analogy for Cylindrical Transformations When r and z are theta Independent
Explanation
The animation explains the space for . When the shape is -simple or the shape is already split into -simple regions, each -infinitesimal ribbon in -plane forms an infinitesimal rectangular solid in -space that transforms to a shell in -space. So in these cases, it is easier to investigate -plane and set up the integral there; we can move to either end since a full rotation is done independently from the other variables.