Bourbaki

Corollary 5

Tag 0CCA, permanent. Cite it as [Bourbaki, Tag 0CCA].

General Topology, chapter X, § 2. Equicontinuous sets

Let X be a topological space, let Y, Z be two uniform spaces and let H be an equicontinuous set of mappings of Y into Z. If H, C(X;Y)\mathscr{C}(X; Y) and C(X;Z)\mathscr{C}(X; Z) are endowed with the topology of pointwise convergence, then the mapping (u,v)→u∘v(u, v) \to u \circ v of H×C(X;Y)H \times \mathscr{C}(X; Y) into C(X;Z)\mathscr{C}(X; Z) is continuous.

We have to show that, for each x∈Xx \in X, the mapping (u,v)→u(v(x))(u, v) \to u(v(x)) of H×C(X;Y)H \times \mathscr{C}(X; Y) into Z is continuous. Now v→v(x)v \to v(x) is continuous on H (§ 1, no. 2, Remark 6), and it follows from Corollary 4 that (u,y)→u(y)(u, y) \to u(y) is a continuous mapping of H×YH \times Y into Z; since (u,v)→u(v(x))(u, v) \to u(v(x)) is the composition of (u,y)→u(y)(u, y) \to u(y) and (u,v)→(u,v(x))(u, v) \to (u, v(x)), the result is proved.

The following proposition and its corollary are the analogues of Corollaries 3 and 4 of Proposition 1 for uniformly equicontinuous sets of mappings:

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

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