Shoes and Socks Principle

The shoes and socks principle describes how Invertible Elements interact with Binary Operations:

• $x^{-1}\star y^{-1}=(y\star x)^{-1}$

The name derives from the following everyday fact: if you want to put your shoes and socks on, you need to first put on your socks, then your shoes. If you want to invert this operation, you need to first take off your shoes, then your socks.