Master Calculus! Get instant help on “I Aced Calculus AP” App. Hundreds of flashcards and practice questions at your fingertips. Download now on the App Store and Google Play.

Derivative of $\ln(x^2)$

In this article, we will be showing that:

\[\begin{align*} \dfrac{d}{dx}(\ln(x^2)) = \boxed{\dfrac2x}. \end{align*}\]

To prove this, we will use the Chain Rule. Recalling the formula for the Chain Rule, we find that the Chain Rule states that:

\[\begin{align*} \dfrac{d}{dx}(f(g(x))) = f'(g(x)) \cdot g'(x). \end{align*}\]

Where $f(x)$ and $g(x)$ are differentiable functions. Using this formula, we let $f(x) = \ln(x)$ and $g(x) = x^2$ so that $f(g(x)) = \ln(g(x)) = \ln(x^2)$. We are able to use the Chain Rule with these functions, as they are differentiable.

To plug these values into the Chain Rule, we need to calculate their derivatives. We can use the formula for the derivative of $\ln(x)$ for $f(x)$, and we can use the Power Rule for $g(x)$:

\[\begin{align*} \dfrac{d}{dx}(\ln(x)) = \dfrac1x \;\;\;\;\;\;\;\;\;\;\;\;\;\;\; \dfrac{d}{dx}(x^n)= nx^{(n-1)} \end{align*}\]

Using this, we find:

\[\begin{align*} f(x) = \ln(x) &\longrightarrow f'(x) = \dfrac1x,\\ g(x) = x^2 &\longrightarrow g'(x) = 2x. \end{align*}\]

Plugging these values into the Chain Rule, we find:

\[\begin{align*} \dfrac{d}{dx}(\ln(x^2)) = f'(g(x)) \cdot g'(x)\\ \dfrac{d}{dx}(\ln(x^2)) = \dfrac{1}{g(x)} \cdot 2x\\ \dfrac{d}{dx}(\ln(x^2)) = \dfrac{1}{x^2} \cdot 2x\\ \dfrac{d}{dx}(\ln(x^2)) = \boxed{\dfrac{2}{x}}. \end{align*}\]


NEED QUICK

CALC HELP?

Download the I Aced Calculus App today!

ALL Calc Topics, 1000+ of PRACTICE questions


Related Problems

NEED QUICK

  • ALL Calc Topics
    AB and BC
  • 1000+
    PRACTICE questions
  • 400+ FLASHCARDS
  • VIDEO tutorials

CALC HELP?

Download the I Aced Calculus App today!