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How to Differentiate Logarithms

The logarithmic function represents a value that mathematicians have "defined to be" the anti-derivative of 1 / X. Differentiating these functions is often challenging, as the process of differentiating a logarithmic function is actually proving that the anti-derivative of 1 divided by the numerical expression in the logarithm is the derivative of the same logarithm. Proving that 1 / x is, in fact, the anti-derivative of ln(x) provides a pathway for proving a large family of rational functions to be the derivative of ln(x).

Instructions

    • 1

      Place the argument of the logarithmic function to be differentiated into the denominator of a fraction under the number one. Example, ln(x - 2) -> 1 / x - 2.

    • 2

      Place the expression into an integral with respect to "x". For example, ∫ 1 / x-2 dx.

    • 3

      Perform a "u-substitution" for the expression in the denominator. For example, x - 2 = u.

    • 4

      Take the derivative of "u." For example, u = x - 2 -> du / dx = 1. The derivative of X - 2 is 1.

    • 5

      Solve the differential equation for dx. For example, du / dx = 1 -> du = dx. Multiply the equation on both sides by dx.

    • 6

      Substitute "u" and "du" into the original expression. Substituting "u" for x - 2 -> 1 / x - 2 = 1 / u and substituting du for dx, then ∫ 1 / d - 2 dx -> ∫ 1 / u du.

    • 7

      Integrate the simplified integral: ∫ 1 / u du = Ln(U).

    • 8

      Substitute the original terms. U was defined as x - 2 earlier, and therefore, Ln(u) = ln(x - 2). This successful u-substitution proves that the anti-derivative of 1 / x - 2 is, in fact, ln(x - 2). Due to their inverse natures, integration and differentiation, this proves that the derivative of ln(x -2 ) is equal to 1 / x - 2. This process works with any logarithmic function.

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