Calculus Examples

$y = \frac{x}{\sin (x) + \cos (x)}$

Step 1

Differentiate both sides of the equation.

$\frac{d}{d x} (y) = \frac{d}{d x} (\frac{x}{\sin (x) + \cos (x)})$

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 $f (x) = x$ and $g (x) = \sin (x) + \cos (x)$ .

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

Step 3.2

Differentiate.

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Step 3.2.1

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

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

Step 3.2.2

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

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

Step 3.2.3

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

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

Step 3.3

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

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

Step 3.4

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

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

Step 3.5

Simplify.

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Step 3.5.1

Apply the distributive property.

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

Step 3.5.2

Multiply $- x (- \sin (x))$ .

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Step 3.5.2.1

Multiply $- 1$ by $- 1$ .

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

Step 3.5.2.2

Multiply $x$ by $1$ .

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

Step 3.5.3

Reorder terms.

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

Step 3.5.4

Factor $- 1$ out of $- x \cos (x)$ .

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

Step 3.5.5

Factor $- 1$ out of $x \sin (x)$ .

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

Step 3.5.6

Factor $- 1$ out of $- (x \cos (x)) - (- x \sin (x))$ .

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

Step 3.5.7

Factor $- 1$ out of $\sin (x)$ .

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

Step 3.5.8

Factor $- 1$ out of $- (x \cos (x) - x \sin (x)) - 1 (- \sin (x))$ .

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

Step 3.5.9

Factor $- 1$ out of $\cos (x)$ .

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

Step 3.5.10

Factor $- 1$ out of $- (x \cos (x) - x \sin (x) - \sin (x)) - 1 (- \cos (x))$ .

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

Step 3.5.11

Rewrite $- (x \cos (x) - x \sin (x) - \sin (x) - \cos (x))$ as $- 1 (x \cos (x) - x \sin (x) - \sin (x) - \cos (x))$ .

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

Step 3.5.12

Move the negative in front of the fraction.

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

Step 4

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

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

Step 5

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

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