What are the classic jokes in the field of mathematics?

A math professor at a British university found that his sewer was blocked, so he hired a plumber to repair it. After 30 minutes, the water pipe was clear. The professor was quite satisfied with the plumber's performance, but when he saw the bill, he couldn't help shouting, "What! In just 30 minutes, the money you collected is enough for my monthly income 1/3! I want to be a plumber! " . The plumber said, "You can go now. Our company is recruiting people, including training. But you have to say that you just graduated from primary school. The company doesn't like people with too high academic qualifications. " So the professor took part in the training and became a plumber. His income tripled at once. He is much happier than before.

A few years later, the company suddenly decided to raise the educational level of plumbers to junior high school graduation, and required its workers to attend night classes. The first class at night school is math. The teacher wanted to see how good the foundation of these plumbers was first, so he randomly selected a person to write the formula of circular area. The professor was chosen, but after working as a plumber for so many years, he forgot that the formula of circular area is π * r 2. So he had to deduce it from the beginning: infinitely divide the circle and then integrate it. But the result he got was negative π * r 2. The professor started again awkwardly and the result was still negative. Embarrassed, he turned to dozens of plumbers sitting in the classroom for help. I saw these colleagues whispering to each other and said to him one after another: exchange the upper and lower limits of integral.

During the American presidential campaign from 65438 to 0972, Nixon claimed that he slowed down the acceleration of inflation during his tenure. This made Nixon the first national leader in history to prove his talent with the third derivative.

A math professor at Moscow University jumped to Harvard and was asked to teach mathematical analysis as soon as he arrived, so he ran to ask other professors, "What should I teach in this course?" Others told him, "just teach some limits, continuity, differentiability, and add some indefinite integrals." The next day, he ran over and asked other professors, "What should I teach in the second class? 」