Calculus Examples

$y = \frac{3 - \cos (x)}{6 + \cos (x)}$

Step 1

Differentiate both sides of the equation.

$\frac{d}{d x} (y) = \frac{d}{d x} (\frac{3 - \cos (x)}{6 + \cos (x)})$

Step 2

The derivative of $y$ with respect to $x$ is $y'$ .

$y'$

Step 3

Differentiate the right side of the equation.

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Step 3.1

Differentiate using the Quotient Rule which states that $\frac{d}{d x} [\frac{f (x)}{g (x)}]$ is $\frac{g (x) \frac{d}{d x} [f (x)] - f (x) \frac{d}{d x} [g (x)]}{{g (x)}^{2}}$ where $f (x) = 3 - \cos (x)$ and $g (x) = 6 + \cos (x)$ .

$\frac{(6 + \cos (x)) \frac{d}{d x} [3 - \cos (x)] - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.2

Differentiate.

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Step 3.2.1

By the Sum Rule, the derivative of $3 - \cos (x)$ with respect to $x$ is $\frac{d}{d x} [3] + \frac{d}{d x} [- \cos (x)]$ .

$\frac{(6 + \cos (x)) (\frac{d}{d x} [3] + \frac{d}{d x} [- \cos (x)]) - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.2.2

Since $3$ is constant with respect to $x$ , the derivative of $3$ with respect to $x$ is $0$ .

$\frac{(6 + \cos (x)) (0 + \frac{d}{d x} [- \cos (x)]) - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.2.3

Add $0$ and $\frac{d}{d x} [- \cos (x)]$ .

$\frac{(6 + \cos (x)) \frac{d}{d x} [- \cos (x)] - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.2.4

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

$\frac{(6 + \cos (x)) (- \frac{d}{d x} [\cos (x)]) - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.3

The derivative of $\cos (x)$ with respect to $x$ is $- \sin (x)$ .

$\frac{(6 + \cos (x)) (- - \sin (x)) - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.4

Differentiate.

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Step 3.4.1

Multiply $- 1$ by $- 1$ .

$\frac{(6 + \cos (x)) (1 \sin (x)) - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.4.2

Multiply $\sin (x)$ by $1$ .

$\frac{(6 + \cos (x)) \sin (x) - (3 - \cos (x)) \frac{d}{d x} [6 + \cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.4.3

By the Sum Rule, the derivative of $6 + \cos (x)$ with respect to $x$ is $\frac{d}{d x} [6] + \frac{d}{d x} [\cos (x)]$ .

$\frac{(6 + \cos (x)) \sin (x) - (3 - \cos (x)) (\frac{d}{d x} [6] + \frac{d}{d x} [\cos (x)])}{{(6 + \cos (x))}^{2}}$

Step 3.4.4

Since $6$ is constant with respect to $x$ , the derivative of $6$ with respect to $x$ is $0$ .

$\frac{(6 + \cos (x)) \sin (x) - (3 - \cos (x)) (0 + \frac{d}{d x} [\cos (x)])}{{(6 + \cos (x))}^{2}}$

Step 3.4.5

Add $0$ and $\frac{d}{d x} [\cos (x)]$ .

$\frac{(6 + \cos (x)) \sin (x) - (3 - \cos (x)) \frac{d}{d x} [\cos (x)]}{{(6 + \cos (x))}^{2}}$

Step 3.5

The derivative of $\cos (x)$ with respect to $x$ is $- \sin (x)$ .

$\frac{(6 + \cos (x)) \sin (x) - (3 - \cos (x)) (- \sin (x))}{{(6 + \cos (x))}^{2}}$

Step 3.6

Multiply.

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Step 3.6.1

Multiply $- 1$ by $- 1$ .

$\frac{(6 + \cos (x)) \sin (x) + 1 (3 - \cos (x)) \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 3.6.2

Multiply $3 - \cos (x)$ by $1$ .

$\frac{(6 + \cos (x)) \sin (x) + (3 - \cos (x)) \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 3.7

Simplify.

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Step 3.7.1

Apply the distributive property.

$\frac{6 \sin (x) + \cos (x) \sin (x) + (3 - \cos (x)) \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 3.7.2

Apply the distributive property.

$\frac{6 \sin (x) + \cos (x) \sin (x) + 3 \sin (x) - \cos (x) \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 3.7.3

Simplify the numerator.

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Step 3.7.3.1

Combine the opposite terms in $6 \sin (x) + \cos (x) \sin (x) + 3 \sin (x) - \cos (x) \sin (x)$ .

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Step 3.7.3.1.1

Subtract $\cos (x) \sin (x)$ from $\cos (x) \sin (x)$ .

$\frac{6 \sin (x) + 0 + 3 \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 3.7.3.1.2

Add $6 \sin (x)$ and $0$ .

$\frac{6 \sin (x) + 3 \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 3.7.3.2

Add $6 \sin (x)$ and $3 \sin (x)$ .

$\frac{9 \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 4

Reform the equation by setting the left side equal to the right side.

$y' = \frac{9 \sin (x)}{{(6 + \cos (x))}^{2}}$

Step 5

Replace $y'$ with $\frac{d y}{d x}$ .

$\frac{d y}{d x} = \frac{9 \sin (x)}{{(6 + \cos (x))}^{2}}$