Section 1: Problem 9 Solution
Working problems is a crucial part of learning mathematics. No one can learn topology merely by poring over the definitions, theorems, and examples that are worked out in the text. One must work part of it out for oneself. To provide that opportunity is the purpose of the exercises.
James R. Munkres
Formulate and prove DeMorgan’s laws for arbitrary unions and intersections.
The first law:
. The second law:
. The proof is similar to the first problem.