How does Spivak Calculus prove that functions are equal to their Taylor Series?

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I have read through Spivak's Calculus, however I am stuck on one detail. Spivak has shown that Taylor series have radii of convergence, and then gives useful formulae for certain common functions such as exp, sin, ... etc. However, I've had a hard time finding where he explicitly shows that these functions are equal to their series in the radius of convergence.