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MathNet 2023-part-05 — 191 problems (EN–VI) Question 86

Math Olympiad Vault · MathNet 2023-part-05 — 191 problems (EN–VI)

Question 86

Let $G = \{f : [0, 1] \to [0, 1] \mid f \text{ is one to one and continuous}\}$, and $\circ$ be the function composition; $(G, \circ)$ is a group.

a) Give an example of an infinite subgroup $H$ of $G$, which contains nonincreasing functions and $H \neq G$.

b) Let $H$ be a finite subgroup of $G$. Prove that $H$ has at most 2 elements.