Calculus Examples

$x = \sqrt{\frac{1 + \cos (θ)}{1 - \cos (θ)}}$

Step 1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{\frac{1 + \cos (θ)}{1 - \cos (θ)}}$ as ${(\frac{1 + \cos (θ)}{1 - \cos (θ)})}^{\frac{1}{2}}$ .

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

Step 2

Differentiate using the chain rule, which states that $\frac{d}{d θ} [f (g (θ))]$ is $f' (g (θ)) g' (θ)$ where $f (θ) = θ^{\frac{1}{2}}$ and $g (θ) = \frac{1 + \cos (θ)}{1 - \cos (θ)}$ .

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Step 2.1

To apply the Chain Rule, set $u$ as $\frac{1 + \cos (θ)}{1 - \cos (θ)}$ .

$\frac{d}{d u} [u^{\frac{1}{2}}] \frac{d}{d θ} [\frac{1 + \cos (θ)}{1 - \cos (θ)}]$

Step 2.2

Differentiate using the Power Rule which states that $\frac{d}{d u} [u^{n}]$ is $n u^{n - 1}$ where $n = \frac{1}{2}$ .

$\frac{1}{2} u^{\frac{1}{2} - 1} \frac{d}{d θ} [\frac{1 + \cos (θ)}{1 - \cos (θ)}]$

Step 2.3

Replace all occurrences of $u$ with $\frac{1 + \cos (θ)}{1 - \cos (θ)}$ .

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

Step 3

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

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

Step 4

Combine $- 1$ and $\frac{2}{2}$ .

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

Step 5

Combine the numerators over the common denominator.

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

Step 6

Simplify the numerator.

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Step 6.1

Multiply $- 1$ by $2$ .

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

Step 6.2

Subtract $2$ from $1$ .

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

Step 7

Move the negative in front of the fraction.

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

Step 8

Differentiate using the Quotient Rule which states that $\frac{d}{d θ} [\frac{f (θ)}{g (θ)}]$ is $\frac{g (θ) \frac{d}{d θ} [f (θ)] - f (θ) \frac{d}{d θ} [g (θ)]}{{g (θ)}^{2}}$ where $f (θ) = 1 + \cos (θ)$ and $g (θ) = 1 - \cos (θ)$ .

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

Step 9

Differentiate.

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Step 9.1

By the Sum Rule, the derivative of $1 + \cos (θ)$ with respect to $θ$ is $\frac{d}{d θ} [1] + \frac{d}{d θ} [\cos (θ)]$ .

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

Step 9.2

Since $1$ is constant with respect to $θ$ , the derivative of $1$ with respect to $θ$ is $0$ .

$\frac{1}{2} {(\frac{1 + \cos (θ)}{1 - \cos (θ)})}^{- \frac{1}{2}} \frac{(1 - \cos (θ)) (0 + \frac{d}{d θ} [\cos (θ)]) - (1 + \cos (θ)) \frac{d}{d θ} [1 - \cos (θ)]}{{(1 - \cos (θ))}^{2}}$

Step 9.3

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

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

Step 10

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

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

Step 11

Differentiate.

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Step 11.1

By the Sum Rule, the derivative of $1 - \cos (θ)$ with respect to $θ$ is $\frac{d}{d θ} [1] + \frac{d}{d θ} [- \cos (θ)]$ .

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

Step 11.2

Since $1$ is constant with respect to $θ$ , the derivative of $1$ with respect to $θ$ is $0$ .

$\frac{1}{2} {(\frac{1 + \cos (θ)}{1 - \cos (θ)})}^{- \frac{1}{2}} \frac{(1 - \cos (θ)) (- \sin (θ)) - (1 + \cos (θ)) (0 + \frac{d}{d θ} [- \cos (θ)])}{{(1 - \cos (θ))}^{2}}$

Step 11.3

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

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

Step 11.4

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

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

Step 11.5

Multiply.

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Step 11.5.1

Multiply $- 1$ by $- 1$ .

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

Step 11.5.2

Multiply $1 + \cos (θ)$ by $1$ .

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

Step 12

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

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

Step 13

Combine fractions.

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Step 13.1

Multiply $\frac{(1 - \cos (θ)) (- \sin (θ)) + (1 + \cos (θ)) (- \sin (θ))}{{(1 - \cos (θ))}^{2}}$ by $\frac{1}{2}$ .

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

Step 13.2

Move $2$ to the left of ${(1 - \cos (θ))}^{2}$ .

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

Step 14

Simplify.

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Step 14.1

Change the sign of the exponent by rewriting the base as its reciprocal.

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

Step 14.2

Apply the product rule to $\frac{1 - \cos (θ)}{1 + \cos (θ)}$ .

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

Step 14.3

Apply the distributive property.

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

Step 14.4

Apply the distributive property.

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

Step 14.5

Combine terms.

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Step 14.5.1

Multiply $- 1$ by $1$ .

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

Step 14.5.2

Rewrite $- 1 \sin (θ)$ as $- \sin (θ)$ .

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

Step 14.5.3

Multiply $- 1$ by $- 1$ .

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

Step 14.5.4

Multiply $\cos (θ)$ by $1$ .

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

Step 14.5.5

Multiply $- 1$ by $1$ .

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

Step 14.5.6

Rewrite $- 1 \sin (θ)$ as $- \sin (θ)$ .

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

Step 14.5.7

Subtract $\sin (θ)$ from $- \sin (θ)$ .

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

Step 14.5.8

Add $\cos (θ) \sin (θ)$ and $\cos (θ) (- \sin (θ))$ .

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Step 14.5.8.1

Reorder $\cos (θ)$ and $- 1$ .

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

Step 14.5.8.2

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

$\frac{0 - 2 \sin (θ)}{2 {(1 - \cos (θ))}^{2}} \cdot \frac{{(1 - \cos (θ))}^{\frac{1}{2}}}{{(1 + \cos (θ))}^{\frac{1}{2}}}$

Step 14.5.9

Subtract $2 \sin (θ)$ from $0$ .

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

Step 14.5.10

Cancel the common factor of $- 2$ and $2$ .

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Step 14.5.10.1

Factor $2$ out of $- 2 \sin (θ)$ .

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

Step 14.5.10.2

Cancel the common factors.

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Step 14.5.10.2.1

Factor $2$ out of $2 {(1 - \cos (θ))}^{2}$ .

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

Step 14.5.10.2.2

Cancel the common factor.

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

Step 14.5.10.2.3

Rewrite the expression.

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

Step 14.5.11

Move the negative in front of the fraction.

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

Step 14.5.12

Multiply $\frac{{(1 - \cos (θ))}^{\frac{1}{2}}}{{(1 + \cos (θ))}^{\frac{1}{2}}}$ by $\frac{\sin (θ)}{{(1 - \cos (θ))}^{2}}$ .

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

Step 14.5.13

Move ${(1 - \cos (θ))}^{\frac{1}{2}}$ to the denominator using the negative exponent rule $b^{n} = \frac{1}{b^{- n}}$ .

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

Step 14.5.14

Multiply ${(1 - \cos (θ))}^{2}$ by ${(1 - \cos (θ))}^{- \frac{1}{2}}$ by adding the exponents.

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Step 14.5.14.1

Move ${(1 - \cos (θ))}^{- \frac{1}{2}}$ .

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

Step 14.5.14.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

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

Step 14.5.14.3

To write $2$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

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

Step 14.5.14.4

Combine $2$ and $\frac{2}{2}$ .

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

Step 14.5.14.5

Combine the numerators over the common denominator.

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

Step 14.5.14.6

Simplify the numerator.

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Step 14.5.14.6.1

Multiply $2$ by $2$ .

$- \frac{\sin (θ)}{{(1 + \cos (θ))}^{\frac{1}{2}} {(1 - \cos (θ))}^{\frac{- 1 + 4}{2}}}$

Step 14.5.14.6.2

Add $- 1$ and $4$ .

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