Let be the set of all calendar dates from 4/30/1789 to 9/25/2014.
Let be the set of names of U.S. presidents.
Let be the set of names of first ladies of the U.S.
Consider the following two functions where is the name of the president of the U.S. on date (the incumbent on inauguration days, to avoid ambiguity) and where is the name of the first lady of the U.S. during the presidency of president .
1. Can the composition of pres o lady be defined? What about lady o pres ?
2. Which of the following functional inverses exist and which do not?
pres -1 , lady-1, (lady o pres) -1, (pres o lady) -1