One day,e^x sees X^2 running down the street in a panic.
"What's wrong?" asks e^x .
"There's a Differential Operator in town!" yells X^2 . "If I run into him too many times, I'll disappear!"
"Don't worry," responds e^x . "I'll go have a chat with him. No, don't worry about me -- he can't hurt me. After all, I'm e^x ."
So e^x walks down the street to the Differential Operator. "My friend tells me you're a Differential Operator," says pompously. "Well, I'm e^x."
"Pleased to meet you e^x, ," says the Differential Operator. "I'm d/dt ."
