Logarithmic Differenation

What is Logarithmic Differenation?

Logarithmic differentiation is a technique that allows us to differentiate functions that cannot be directly differentiated using the standard rules of calculus. It is based on the property that the derivative of the logarithm of a function is equal to the derivative of the function divided by the function itself.

Let's say we want to differentiate the function $f(x) = x^3$. Using the power rule for derivatives, we can write the derivative as:

$$\frac{d}{dx} x^3 = 3x^2$$

Now, let's say we want to differentiate the function $g(x) = \ln(x^3)$. We can use logarithmic differentiation to find the derivative of $g(x)$ as follows:

$$\frac{d}{dx} \ln(x^3) = \frac{1}{x^3} \cdot \frac{d}{dx} x^3$$

Using the power rule, we can simplify this expression to:

$$\frac{d}{dx} \ln(x^3) = \frac{3x^2}{x^3} = \frac{3}{x}$$

So, the derivative of $\ln(x^3)$ is $\frac{3}{x}$. Note that this is the same as the derivative of $f(x)$ divided by $f(x)$ itself:

$$\frac{\frac{d}{dx} x^3}{x^3} = \frac{3x^2}{x^3} = \frac{3}{x}$$

This is the basic idea behind logarithmic differentiation. It allows us to differentiate functions that cannot be directly differentiated using the standard rules of calculus by expressing them in terms of logarithms and applying the property of the derivative of the logarithm.