I've been reading Enderton's Mathematical Introduction to Logic. One of the exercises on Compactness theorem requires the proof that the following corollary
[(Corollary 17A) Suppose $\Sigma \models \tau$, then there is a finite $\Sigma_0 \subseteq \Sigma$ such that $\Sigma_0 \models \tau$. ]
is equivalent to Compactness Theorem.
Can any one give me a hint on how to prove CT from this statement?