# 2019-08 Group action

Let $$G$$ be a group acting by isometries on a proper geodesic metric space $$X$$. Here $$X$$ being proper means that every closed bounded subset of $$X$$ is compact. Suppose this action is proper and cocompact,. Here, the action is said to be proper if for all compact subsets $$B \subset X$$, the set $\{g \in G | g(B) \cap B \neq \emptyset \}$ is finite. The quotient space $$X/G$$ is obtained from $$X$$ by identifying any two points $$x, y$$ if and only if there exists $$g \in G$$ such that $$gx = y$$, and equipped with the quotient topology. Then the action of $$G$$ on $$X$$ is said to be cocompact if $$X/G$$ is compact. Under these assumptions, show that $$G$$ is finitely generated.

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