Mathematics Joke (Requires Calculus)

After a stunningly successful career, a mathematics professor went insane, thinking he was the differentiation operator. At the asylum he terrorized the other patients. He would run up to them and scream,

"I differentiate you! I differentiate you!"

The other patients would huddle in fear and begin sobbing. One day a new patient arrived and the insane professor started screaming at him,

"I differentiate you! I differentiate you!"

The patient didn't respond in the slightest. The professor screamed again,

"I differentiate you! I differentiate you!"

The new patient finally replied,

"Differentiate me all you want. I'm e to the x!"