In most of exercises of textbooks when ask me to differentiate f using logarithmic differentiation(adsbygoogle = window.adsbygoogle || []).push({});

some time f(x) = 0 for some values of x , so I I used logarithmic Differentiation for all x in domain of f , such that f(x) not equal zero. then prove using the definition directly that for these x the formula obtained , or prove that it doesn't exist for this zero. Is that right because most of books I had seen when give an examples of logarithmic differentiation don't care for this point I don't Know that this not important point or not.

Thanks

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# A question in logarithmic differentiation

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