Calculus Examples

$\ln (x) \cdot \ln (10 x)$

Step 1

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = \ln (x)$ and $g (x) = \ln (10 x)$ .

$\ln (x) \frac{d}{d x} [\ln (10 x)] + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Step 2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \ln (x)$ and $g (x) = 10 x$ .

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To apply the Chain Rule, set $u$ as $10 x$ .

$\ln (x) (\frac{d}{d u} [\ln (u)] \frac{d}{d x} [10 x]) + \ln (10 x) \frac{d}{d x} [\ln (x)]$

The derivative of $\ln (u)$ with respect to $u$ is $\frac{1}{u}$ .

$\ln (x) (\frac{1}{u} \frac{d}{d x} [10 x]) + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Replace all occurrences of $u$ with $10 x$ .

$\ln (x) (\frac{1}{10 x} \frac{d}{d x} [10 x]) + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Step 3

Differentiate.

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Combine $\frac{1}{10 x}$ and $\ln (x)$ .

$\frac{\ln (x)}{10 x} \frac{d}{d x} [10 x] + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Since $10$ is constant with respect to $x$ , the derivative of $10 x$ with respect to $x$ is $10 \frac{d}{d x} [x]$ .

$\frac{\ln (x)}{10 x} (10 \frac{d}{d x} [x]) + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Simplify terms.

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Combine $10$ and $\frac{\ln (x)}{10 x}$ .

$\frac{10 \ln (x)}{10 x} \frac{d}{d x} [x] + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Cancel the common factor of $10$ .

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Cancel the common factor.

$\frac{10 \ln (x)}{10 x} \frac{d}{d x} [x] + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Rewrite the expression.

$\frac{\ln (x)}{x} \frac{d}{d x} [x] + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$\frac{\ln (x)}{x} \cdot 1 + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Multiply $\frac{\ln (x)}{x}$ by $1$ .

$\frac{\ln (x)}{x} + \ln (10 x) \frac{d}{d x} [\ln (x)]$

Step 4

The derivative of $\ln (x)$ with respect to $x$ is $\frac{1}{x}$ .

$\frac{\ln (x)}{x} + \ln (10 x) \frac{1}{x}$

Step 5

Combine $\ln (10 x)$ and $\frac{1}{x}$ .

$\frac{\ln (x)}{x} + \frac{\ln (10 x)}{x}$

Step 6

Simplify.

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Combine the numerators over the common denominator.

$\frac{\ln (x) + \ln (10 x)}{x}$

Use the product property of logarithms, $\log_{b} (x) + \log_{b} (y) = \log_{b} (x y)$ .

$\frac{\ln (x (10 x))}{x}$

Rewrite using the commutative property of multiplication.

$\frac{\ln (10 x \cdot x)}{x}$

Multiply $x$ by $x$ by adding the exponents.

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Move $x$ .

$\frac{\ln (10 (x \cdot x))}{x}$

Multiply $x$ by $x$ .

$\frac{\ln (10 x^{2})}{x}$