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Thread: du/u

  1. #1
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    du/u

    Can somebody tell me what this means? dy/dx means a small change in y with respect to a small change in x. du/u means a small change in u with respect to no change in u?
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  2. #2
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    Don't reply to this. I have worked it out. In the conext it was just a bit of algebraic manipulation.
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  3. #3
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    It's just a shorthand way of writing the chain rule in reverse (for integration, the reverse process of differentiation).


    $\displaystyle \int{f\left(g(x)\right)\,g'(x)\,dx} = \int{f(u)\,\frac{du}{dx}\,dx} = \int{f(u)\,du}$ by making the substitution $\displaystyle u = g(x)$.


    In your case, $\displaystyle f\left(g(x)\right) = \frac{1}{g(x)}$.
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