When It Pays to Know Some Calculus
A slightly deranged mathematician (possibly redundant) gets on a city bus and then starts threatening everybody: "I'll integrate you! I'll differentiate you!!!"
All of the people on the bus panic, rush off the bus, and run away...except for one woman who remains calmly sitting in her seat.
The mathematician walks up to her and says: "Aren't you scared, I'll integrate you, I'll differentiate you!!!"
The woman calmly answers: "No, I am not scared, I am ex."