Let (K,d)(K,d) be a and let FC(K,R)\mathcal{F}\subseteq C(K,\mathbb{R}) be a family of . Assume:

  • F\mathcal{F} is on KK, and
  • F\mathcal{F} is on KK (for each xKx\in K, supfFf(x)<\sup_{f\in\mathcal{F}}|f(x)|<\infty).

Lemma: Then F\mathcal{F} is on KK; i.e., there exists M<M<\infty such that

f(x)Mfor all fF, xK.|f(x)|\le M\quad \text{for all } f\in\mathcal{F},\ x\in K.
Remarks

This lemma is a standard step in the proof of the .