Four-Function 2-class Calculator

I wrote in a bunch of comments explaining what i was doing/trying to do.
At the bottom I was trying to figure out how to make the program
recognize if the user inputted a false function (typed it wrong), but
it wasn't running properly, so i turned it into a comment
Finding square roots and radicals, and package info
Udemy tutorials 9 & 10 with package info
Package info
Created a new package and class for my Book
added a second option to Dan's app

not executing properly yet
deleted a copy of tutorial9