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July 28th, 2013, 07:32 AM   #1
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chain rule- constant rule

How do we get constant rule as a VARIATION OF CHAIN RULE????

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July 30th, 2013, 06:10 PM   #2
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Re: chain rule- constant rule

Why should we? The "constant rule" (I assume you mean "the derivative of a constant function is 0 for all x") is much more fundamental than the chain rule.

I suppose you could argue that, if f(x)= a for all x, then h(x)= f(g(x))= a for all x and any g. By the chain rule, . But clearly, h(x)= f(x) for all x so . That is, we have for all g. Since for all functions, g, is NOT true, we must have . But that seems like using a sledgehammer to kill a fly.
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