(n.) The act of deriving equations just for the sake of deriving them, at no apparent gain to
the student.
In verb form, to mathturbate is to perform such menial
mathematical labor.
mathturbatory: characterized by
excessive mathturbation
"
The professor spent three hours deriving the equation
on the board because he thought it would help us
understand the concept better; really, however, he just confused us with his senseless mathturbation."
"The homework problem required hours of mathturbation, with the end result being a simple identity that appears in the index of every text."