* [Presentation on exercise 12](https://www.azimuthproject.org/azimuth/files/roman-exercise-12.pdf), by David Tanzer, 5/3/2020

The exercise amounts to proving the definition of the left and right [whiskering](https://proofwiki.org/wiki/Definition:Whiskering) of a functor and a natural transformation.

* Right whiskering = natural transformation followed by functor
* Left whiskering = functor followed by natural transformation

In this imagery, the functor is the "whisker" in the diagram, and the natural transformation is the cat.