Joke: Why does the mathematician never plant x2 + 1 plants?
Punch line: It's hard to grow plants with imaginary roots.
Joke: What is one math problem that no German person can get wrong?
Punch line: Do you know the square root of 81?
Joke: Why did the mathematician name his dog "Cauchy?"
Punch line: He left a residue at every pole.
Joke: Why is the tan function so quick to differentiate?
Punch line: It ends in secs.
Joke: What do you get if you divide the circumference of a jack-o-lantern by its diameter?
Punch line: Pumpkin pi!