mirrorbird(23:50:21)
just before the class is scheduled to end, the professor reappears, and announces "Yes, it is obvious."
mirrorbird(23:50:07)
he sees the professor in his office working on the blackboard which he has covered with mathematics. the student returns and reports to the class.
mirrorbird(23:49:56)
the professor responds "it is obvious." then the professor steps back, stares at the board and ponders for several minutes. Then he turns and walks out of the lecture hall. he is absent for a long time and finally one of the students goes to look for him.
mirrorbird(23:49:26)
JOKE: a mathematics professor is giving a lecture and has made an assertion as part of his presentation. a student, not understanding the basis for the assertion, asks why it is true.