« Section 9: Infinite Sets and the Axiom of Choice

Section 9: Problem 2 Solution »

Section 9: Problem 1 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
Define an injective map without using the choice axiom.
For , .