Calculus Examples

$y = \log_{9} (e^{- x} \cos (π x))$

Step 1

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \log_{9} (x)$ and $g (x) = e^{- x} \cos (π x)$ .

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Step 1.1

To apply the Chain Rule, set $u_{1}$ as $e^{- x} \cos (π x)$ .

$\frac{d}{d u_{1}} [\log_{9} (u_{1})] \frac{d}{d x} [e^{- x} \cos (π x)]$

Step 1.2

The derivative of $\log_{9} (u_{1})$ with respect to $u_{1}$ is $\frac{1}{u_{1} \ln (9)}$ .

$\frac{1}{u_{1} \ln (9)} \frac{d}{d x} [e^{- x} \cos (π x)]$

Step 1.3

Replace all occurrences of $u_{1}$ with $e^{- x} \cos (π x)$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} \frac{d}{d x} [e^{- x} \cos (π x)]$

Step 2

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 $f (x) = e^{- x}$ and $g (x) = \cos (π x)$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} \frac{d}{d x} [\cos (π x)] + \cos (π x) \frac{d}{d x} [e^{- x}])$

Step 3

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

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Step 3.1

To apply the Chain Rule, set $u_{2}$ as $π x$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (\frac{d}{d u_{2}} [\cos (u_{2})] \frac{d}{d x} [π x]) + \cos (π x) \frac{d}{d x} [e^{- x}])$

Step 3.2

The derivative of $\cos (u_{2})$ with respect to $u_{2}$ is $- \sin (u_{2})$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (u_{2}) \frac{d}{d x} [π x]) + \cos (π x) \frac{d}{d x} [e^{- x}])$

Step 3.3

Replace all occurrences of $u_{2}$ with $π x$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) \frac{d}{d x} [π x]) + \cos (π x) \frac{d}{d x} [e^{- x}])$

Step 4

Differentiate.

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Step 4.1

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

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) (π \frac{d}{d x} [x])) + \cos (π x) \frac{d}{d x} [e^{- x}])$

Step 4.2

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

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) (π \cdot 1)) + \cos (π x) \frac{d}{d x} [e^{- x}])$

Step 4.3

Multiply $π$ by $1$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) \frac{d}{d x} [e^{- x}])$

Step 5

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

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Step 5.1

To apply the Chain Rule, set $u_{3}$ as $- x$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (\frac{d}{d u_{3}} [e^{u_{3}}] \frac{d}{d x} [- x]))$

Step 5.2

Differentiate using the Exponential Rule which states that $\frac{d}{d u_{3}} [a^{u_{3}}]$ is $a^{u_{3}} \ln (a)$ where $a$ = $e$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (e^{u_{3}} \frac{d}{d x} [- x]))$

Step 5.3

Replace all occurrences of $u_{3}$ with $- x$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (e^{- x} \frac{d}{d x} [- x]))$

Step 6

Differentiate.

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Step 6.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- x$ with respect to $x$ is $- \frac{d}{d x} [x]$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (e^{- x} (- \frac{d}{d x} [x])))$

Step 6.2

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

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (e^{- x} (- 1 \cdot 1)))$

Step 6.3

Simplify the expression.

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Step 6.3.1

Multiply $- 1$ by $1$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (e^{- x} \cdot - 1))$

Step 6.3.2

Move $- 1$ to the left of $e^{- x}$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (- 1 \cdot e^{- x}))$

Step 6.3.3

Rewrite $- 1 e^{- x}$ as $- e^{- x}$ .

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π) + \cos (π x) (- e^{- x}))$

Step 7

Simplify.

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Step 7.1

Apply the distributive property.

$\frac{1}{e^{- x} \cos (π x) \ln (9)} (e^{- x} (- \sin (π x) π)) + \frac{1}{e^{- x} \cos (π x) \ln (9)} (\cos (π x) (- e^{- x}))$

Step 7.2

Combine terms.

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Step 7.2.1

Combine $e^{- x}$ and $\frac{1}{e^{- x} \cos (π x) \ln (9)}$ .

$\frac{e^{- x}}{e^{- x} \cos (π x) \ln (9)} (- \sin (π x) π) + \frac{1}{e^{- x} \cos (π x) \ln (9)} (\cos (π x) (- e^{- x}))$

Step 7.2.2

Combine $\frac{e^{- x}}{e^{- x} \cos (π x) \ln (9)}$ and $\sin (π x)$ .

$- \frac{e^{- x} \sin (π x)}{e^{- x} \cos (π x) \ln (9)} π + \frac{1}{e^{- x} \cos (π x) \ln (9)} (\cos (π x) (- e^{- x}))$

Step 7.2.3

Combine $π$ and $\frac{e^{- x} \sin (π x)}{e^{- x} \cos (π x) \ln (9)}$ .

$- \frac{π (e^{- x} \sin (π x))}{e^{- x} \cos (π x) \ln (9)} + \frac{1}{e^{- x} \cos (π x) \ln (9)} (\cos (π x) (- e^{- x}))$

Step 7.2.4

Cancel the common factor of $e^{- x}$ .

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Step 7.2.4.1

Cancel the common factor.

$- \frac{π e^{- x} \sin (π x)}{e^{- x} \cos (π x) \ln (9)} + \frac{1}{e^{- x} \cos (π x) \ln (9)} (\cos (π x) (- e^{- x}))$

Step 7.2.4.2

Rewrite the expression.

$- \frac{π \sin (π x)}{\cos (π x) \ln (9)} + \frac{1}{e^{- x} \cos (π x) \ln (9)} (\cos (π x) (- e^{- x}))$

Step 7.2.5

Combine $\cos (π x)$ and $\frac{1}{e^{- x} \cos (π x) \ln (9)}$ .

$- \frac{π \sin (π x)}{\cos (π x) \ln (9)} + \frac{\cos (π x)}{e^{- x} \cos (π x) \ln (9)} (- e^{- x})$

Step 7.2.6

Combine $\frac{\cos (π x)}{e^{- x} \cos (π x) \ln (9)}$ and $e^{- x}$ .

$- \frac{π \sin (π x)}{\cos (π x) \ln (9)} - \frac{\cos (π x) e^{- x}}{e^{- x} \cos (π x) \ln (9)}$

Step 7.2.7

Cancel the common factor of $\cos (π x)$ .

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Step 7.2.7.1

Cancel the common factor.

$- \frac{π \sin (π x)}{\cos (π x) \ln (9)} - \frac{\cos (π x) e^{- x}}{e^{- x} \cos (π x) \ln (9)}$

Step 7.2.7.2

Rewrite the expression.

$- \frac{π \sin (π x)}{\cos (π x) \ln (9)} - \frac{e^{- x}}{e^{- x} \ln (9)}$

Step 7.2.8

Cancel the common factor of $e^{- x}$ .

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Step 7.2.8.1

Cancel the common factor.

$- \frac{π \sin (π x)}{\cos (π x) \ln (9)} - \frac{e^{- x}}{e^{- x} \ln (9)}$

Step 7.2.8.2

Rewrite the expression.

$- \frac{π \sin (π x)}{\cos (π x) \ln (9)} - \frac{1}{\ln (9)}$

Step 7.3

Simplify each term.

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Step 7.3.1

Separate fractions.

$- (\frac{π}{\ln (9)} \cdot \frac{\sin (π x)}{\cos (π x)}) - \frac{1}{\ln (9)}$

Step 7.3.2

Convert from $\frac{\sin (π x)}{\cos (π x)}$ to $\tan (π x)$ .

$- (\frac{π}{\ln (9)} \tan (π x)) - \frac{1}{\ln (9)}$

Step 7.3.3

Combine $\frac{π}{\ln (9)}$ and $\tan (π x)$ .

$- \frac{π \tan (π x)}{\ln (9)} - \frac{1}{\ln (9)}$