Comments by "MC116" (@angelmendez-rivera351) on "Derivative of f(x) = 1/x Using the Limit Definition" video.

  1. You are so wrong. You said that f is differentiable on any interval (a, b) with a < 0 < b. This is not at all true. f is not differentiable at 0, as 0 is not in the domain of f. No theorem is being violated here. f is continuous everywhere in its domain, its domain being R\{0}. f is also continuously differentiable everywhere in its domain. In fact, f is real-analytic everywhere in its domain.
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  2. That just takes longer to do, and requires that you prove the chain rule in the first place. This exercise using the definition is really easy and takes two lines at most.
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