Trigonometry Examples

$\frac{1 - \sin (x)}{1 + \sin (x)} = {(\sec (x) - \tan (x))}^{2}$

Step 1

Subtract ${(\sec (x) - \tan (x))}^{2}$ from both sides of the equation.

$\frac{1 - \sin (x)}{1 + \sin (x)} - {(\sec (x) - \tan (x))}^{2} = 0$

Step 2

Simplify $\frac{1 - \sin (x)}{1 + \sin (x)} - {(\sec (x) - \tan (x))}^{2}$ .

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Step 2.1

Simplify each term.

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Step 2.1.1

Simplify each term.

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Step 2.1.1.1

Rewrite $\sec (x)$ in terms of sines and cosines.

$\frac{1 - \sin (x)}{1 + \sin (x)} - {(\frac{1}{\cos (x)} - \tan (x))}^{2} = 0$

Step 2.1.1.2

Rewrite $\tan (x)$ in terms of sines and cosines.

$\frac{1 - \sin (x)}{1 + \sin (x)} - {(\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)})}^{2} = 0$

Step 2.1.2

Rewrite ${(\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)})}^{2}$ as $(\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)}) (\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)})$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - ((\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)}) (\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.3

Expand $(\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)}) (\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)})$ using the FOIL Method.

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Step 2.1.3.1

Apply the distributive property.

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos (x)} (\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)}) - \frac{\sin (x)}{\cos (x)} (\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.3.2

Apply the distributive property.

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos (x)} \cdot \frac{1}{\cos (x)} + \frac{1}{\cos (x)} (- \frac{\sin (x)}{\cos (x)}) - \frac{\sin (x)}{\cos (x)} (\frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.3.3

Apply the distributive property.

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos (x)} \cdot \frac{1}{\cos (x)} + \frac{1}{\cos (x)} (- \frac{\sin (x)}{\cos (x)}) - \frac{\sin (x)}{\cos (x)} \cdot \frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4

Simplify and combine like terms.

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Step 2.1.4.1

Simplify each term.

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Step 2.1.4.1.1

Multiply $\frac{1}{\cos (x)} \cdot \frac{1}{\cos (x)}$ .

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Step 2.1.4.1.1.1

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

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos (x) \cos (x)} + \frac{1}{\cos (x)} (- \frac{\sin (x)}{\cos (x)}) - \frac{\sin (x)}{\cos (x)} \cdot \frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.1.2

Raise $\cos (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{1} (x) \cos (x)} + \frac{1}{\cos (x)} (- \frac{\sin (x)}{\cos (x)}) - \frac{\sin (x)}{\cos (x)} \cdot \frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.1.3

Raise $\cos (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{1} (x) \cos^{1} (x)} + \frac{1}{\cos (x)} (- \frac{\sin (x)}{\cos (x)}) - \frac{\sin (x)}{\cos (x)} \cdot \frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.1.4

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

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{{\cos (x)}^{1 + 1}} + \frac{1}{\cos (x)} (- \frac{\sin (x)}{\cos (x)}) - \frac{\sin (x)}{\cos (x)} \cdot \frac{1}{\cos (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.1.5

Add $1$ and $1$ .

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

Step 2.1.4.1.2

Rewrite using the commutative property of multiplication.

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

Step 2.1.4.1.3

Multiply $- \frac{1}{\cos (x)} \cdot \frac{\sin (x)}{\cos (x)}$ .

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Step 2.1.4.1.3.1

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

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

Step 2.1.4.1.3.2

Raise $\cos (x)$ to the power of $1$ .

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

Step 2.1.4.1.3.3

Raise $\cos (x)$ to the power of $1$ .

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

Step 2.1.4.1.3.4

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

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

Step 2.1.4.1.3.5

Add $1$ and $1$ .

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

Step 2.1.4.1.4

Multiply $- \frac{\sin (x)}{\cos (x)} \cdot \frac{1}{\cos (x)}$ .

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Step 2.1.4.1.4.1

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

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos (x) \cos (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.4.2

Raise $\cos (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{1} (x) \cos (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.4.3

Raise $\cos (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{1} (x) \cos^{1} (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.4.4

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

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{{\cos (x)}^{1 + 1}} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.4.5

Add $1$ and $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})) = 0$

Step 2.1.4.1.5

Multiply $- \frac{\sin (x)}{\cos (x)} (- \frac{\sin (x)}{\cos (x)})$ .

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Step 2.1.4.1.5.1

Multiply $- 1$ by $- 1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + 1 \frac{\sin (x)}{\cos (x)} \frac{\sin (x)}{\cos (x)}) = 0$

Step 2.1.4.1.5.2

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

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

Step 2.1.4.1.5.3

Multiply $\frac{\sin (x)}{\cos (x)}$ by $\frac{\sin (x)}{\cos (x)}$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin (x) \sin (x)}{\cos (x) \cos (x)}) = 0$

Step 2.1.4.1.5.4

Raise $\sin (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{1} (x) \sin (x)}{\cos (x) \cos (x)}) = 0$

Step 2.1.4.1.5.5

Raise $\sin (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{1} (x) \sin^{1} (x)}{\cos (x) \cos (x)}) = 0$

Step 2.1.4.1.5.6

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

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{{\sin (x)}^{1 + 1}}{\cos (x) \cos (x)}) = 0$

Step 2.1.4.1.5.7

Add $1$ and $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{\cos (x) \cos (x)}) = 0$

Step 2.1.4.1.5.8

Raise $\cos (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{\cos^{1} (x) \cos (x)}) = 0$

Step 2.1.4.1.5.9

Raise $\cos (x)$ to the power of $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{\cos^{1} (x) \cos^{1} (x)}) = 0$

Step 2.1.4.1.5.10

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

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{{\cos (x)}^{1 + 1}}) = 0$

Step 2.1.4.1.5.11

Add $1$ and $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} - \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{\cos^{2} (x)}) = 0$

Step 2.1.4.2

Subtract $\frac{\sin (x)}{\cos^{2} (x)}$ from $- \frac{\sin (x)}{\cos^{2} (x)}$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - 2 \frac{\sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{\cos^{2} (x)}) = 0$

Step 2.1.5

Simplify each term.

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Step 2.1.5.1

Combine $- 2$ and $\frac{\sin (x)}{\cos^{2} (x)}$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} + \frac{- 2 \sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{\cos^{2} (x)}) = 0$

Step 2.1.5.2

Move the negative in front of the fraction.

$\frac{1 - \sin (x)}{1 + \sin (x)} - (\frac{1}{\cos^{2} (x)} - \frac{2 \sin (x)}{\cos^{2} (x)} + \frac{\sin^{2} (x)}{\cos^{2} (x)}) = 0$

Step 2.1.6

Apply the distributive property.

$\frac{1 - \sin (x)}{1 + \sin (x)} - \frac{1}{\cos^{2} (x)} - - \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.1.7

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

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Step 2.1.7.1

Multiply $- 1$ by $- 1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - \frac{1}{\cos^{2} (x)} + 1 \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.1.7.2

Multiply $\frac{2 \sin (x)}{\cos^{2} (x)}$ by $1$ .

$\frac{1 - \sin (x)}{1 + \sin (x)} - \frac{1}{\cos^{2} (x)} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.2

To write $\frac{1 - \sin (x)}{1 + \sin (x)}$ as a fraction with a common denominator, multiply by $\frac{\cos^{2} (x)}{\cos^{2} (x)}$ .

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

Step 2.3

To write $- \frac{1}{\cos^{2} (x)}$ as a fraction with a common denominator, multiply by $\frac{1 + \sin (x)}{1 + \sin (x)}$ .

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

Step 2.4

Write each expression with a common denominator of $(1 + \sin (x)) \cos^{2} (x)$ , by multiplying each by an appropriate factor of $1$ .

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Step 2.4.1

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

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

Step 2.4.2

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

$\frac{(1 - \sin (x)) \cos^{2} (x)}{(1 + \sin (x)) \cos^{2} (x)} - \frac{1 + \sin (x)}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.4.3

Reorder the factors of $(1 + \sin (x)) \cos^{2} (x)$ .

$\frac{(1 - \sin (x)) \cos^{2} (x)}{\cos^{2} (x) (1 + \sin (x))} - \frac{1 + \sin (x)}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.5

Combine the numerators over the common denominator.

$\frac{(1 - \sin (x)) \cos^{2} (x) - (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6

Simplify each term.

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Step 2.6.1

Simplify the numerator.

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Step 2.6.1.1

Apply the distributive property.

$\frac{1 \cos^{2} (x) - \sin (x) \cos^{2} (x) - (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.2

Multiply $\cos^{2} (x)$ by $1$ .

$\frac{\cos^{2} (x) - \sin (x) \cos^{2} (x) - (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.3

Apply the distributive property.

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

Step 2.6.1.4

Multiply $- 1$ by $1$ .

$\frac{\cos^{2} (x) - \sin (x) \cos^{2} (x) - 1 - \sin (x)}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5

Rewrite $\cos^{2} (x) - \sin (x) \cos^{2} (x) - 1 - \sin (x)$ in a factored form.

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Step 2.6.1.5.1

Regroup terms.

$\frac{- \sin (x) + \cos^{2} (x) - \sin (x) \cos^{2} (x) - 1}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.2

Add parentheses.

$\frac{- \sin (x) + \cos^{2} (x) - (\sin (x) \cos^{2} (x)) - 1}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.3

Let $u = \sin (x) \cos^{2} (x)$ . Substitute $u$ for all occurrences of $\sin (x) \cos^{2} (x)$ .

$\frac{- \sin (x) - \sin^{2} (x) - u}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.4

Factor $- 1$ out of $- \sin^{2} (x) - u$ .

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Step 2.6.1.5.4.1

Reorder $- \sin^{2} (x)$ and $- u$ .

$\frac{- \sin (x) - u - \sin^{2} (x)}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.4.2

Factor $- 1$ out of $- u$ .

$\frac{- \sin (x) - (u) - \sin^{2} (x)}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.4.3

Factor $- 1$ out of $- \sin^{2} (x)$ .

$\frac{- \sin (x) - (u) - (\sin^{2} (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.4.4

Factor $- 1$ out of $- (u) - (\sin^{2} (x))$ .

$\frac{- \sin (x) - (u + \sin^{2} (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.5

Replace all occurrences of $u$ with $\sin (x) \cos^{2} (x)$ .

$\frac{- \sin (x) - (\sin (x) \cos^{2} (x) + \sin^{2} (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.6

Factor $\sin (x)$ out of $\sin (x) \cos^{2} (x) + \sin^{2} (x)$ .

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Step 2.6.1.5.6.1

Factor $\sin (x)$ out of $\sin (x) \cos^{2} (x)$ .

$\frac{- \sin (x) - (\sin (x) (\cos^{2} (x)) + \sin^{2} (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.6.2

Factor $\sin (x)$ out of $\sin^{2} (x)$ .

$\frac{- \sin (x) - (\sin (x) (\cos^{2} (x)) + \sin (x) \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.6.3

Factor $\sin (x)$ out of $\sin (x) (\cos^{2} (x)) + \sin (x) \sin (x)$ .

$\frac{- \sin (x) - (\sin (x) (\cos^{2} (x) + \sin (x)))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

$\frac{- \sin (x) - \sin (x) (\cos^{2} (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.7

Factor $- \sin (x)$ out of $- \sin (x) - \sin (x) (\cos^{2} (x) + \sin (x))$ .

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Step 2.6.1.5.7.1

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

$\frac{- \sin (x) (1) - \sin (x) (\cos^{2} (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.1.5.7.2

Factor $- \sin (x)$ out of $- \sin (x) (1) - \sin (x) (\cos^{2} (x) + \sin (x))$ .

$\frac{- \sin (x) (1 + \cos^{2} (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.6.2

Move the negative in front of the fraction.

$- \frac{\sin (x) (1 + \cos^{2} (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.7

To write $\frac{2 \sin (x)}{\cos^{2} (x)}$ as a fraction with a common denominator, multiply by $\frac{1 + \sin (x)}{1 + \sin (x)}$ .

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

Step 2.8

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

$- \frac{\sin (x) (1 + \cos^{2} (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} + \frac{2 \sin (x) (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.9

Combine the numerators over the common denominator.

$\frac{- \sin (x) (1 + \cos^{2} (x) + \sin (x)) + 2 \sin (x) (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10

Simplify each term.

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Step 2.10.1

Simplify the numerator.

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Step 2.10.1.1

Factor $\sin (x)$ out of $- \sin (x) (1 + \cos^{2} (x) + \sin (x)) + 2 \sin (x) (1 + \sin (x))$ .

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Step 2.10.1.1.1

Factor $\sin (x)$ out of $- \sin (x) (1 + \cos^{2} (x) + \sin (x))$ .

$\frac{\sin (x) (- 1 (1 + \cos^{2} (x) + \sin (x))) + 2 \sin (x) (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.1.2

Factor $\sin (x)$ out of $2 \sin (x) (1 + \sin (x))$ .

$\frac{\sin (x) (- 1 (1 + \cos^{2} (x) + \sin (x))) + \sin (x) (2 (1 + \sin (x)))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.1.3

Factor $\sin (x)$ out of $\sin (x) (- 1 (1 + \cos^{2} (x) + \sin (x))) + \sin (x) (2 (1 + \sin (x)))$ .

$\frac{\sin (x) (- 1 (1 + \cos^{2} (x) + \sin (x)) + 2 (1 + \sin (x)))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.2

Apply the distributive property.

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

Step 2.10.1.3

Simplify.

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Step 2.10.1.3.1

Multiply $- 1$ by $1$ .

$\frac{\sin (x) (- 1 - 1 \cos^{2} (x) - 1 \sin (x) + 2 (1 + \sin (x)))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.3.2

Rewrite $- 1 \cos^{2} (x)$ as $- \cos^{2} (x)$ .

$\frac{\sin (x) (- 1 - \cos^{2} (x) - 1 \sin (x) + 2 (1 + \sin (x)))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.3.3

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

$\frac{\sin (x) (- 1 - \cos^{2} (x) - \sin (x) + 2 (1 + \sin (x)))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.4

Apply the distributive property.

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

Step 2.10.1.5

Multiply $2$ by $1$ .

$\frac{\sin (x) (- 1 - \cos^{2} (x) - \sin (x) + 2 + 2 \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.6

Add $- 1$ and $2$ .

$\frac{\sin (x) (1 - \cos^{2} (x) - \sin (x) + 2 \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.7

Add $- \sin (x)$ and $2 \sin (x)$ .

$\frac{\sin (x) (1 - \cos^{2} (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.8

Apply pythagorean identity.

$\frac{\sin (x) (\sin^{2} (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.9

Factor $\sin (x)$ out of $\sin^{2} (x) + \sin (x)$ .

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Step 2.10.1.9.1

Factor $\sin (x)$ out of $\sin^{2} (x)$ .

$\frac{\sin (x) (\sin (x) \sin (x) + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.9.2

Multiply by $1$ .

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

Step 2.10.1.9.3

Factor $\sin (x)$ out of $\sin (x) \sin (x) + \sin (x) \cdot 1$ .

$\frac{\sin (x) (\sin (x) (\sin (x) + 1))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

$\frac{\sin (x) \sin (x) (\sin (x) + 1)}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.10

Combine exponents.

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Step 2.10.1.10.1

Raise $\sin (x)$ to the power of $1$ .

$\frac{\sin^{1} (x) \sin (x) (\sin (x) + 1)}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.10.2

Raise $\sin (x)$ to the power of $1$ .

$\frac{\sin^{1} (x) \sin^{1} (x) (\sin (x) + 1)}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.10.3

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

$\frac{{\sin (x)}^{1 + 1} (\sin (x) + 1)}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.1.10.4

Add $1$ and $1$ .

$\frac{\sin^{2} (x) (\sin (x) + 1)}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.2

Cancel the common factor of $\sin (x) + 1$ and $1 + \sin (x)$ .

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Step 2.10.2.1

Reorder terms.

$\frac{\sin^{2} (x) (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.2.2

Cancel the common factor.

$\frac{\sin^{2} (x) (1 + \sin (x))}{\cos^{2} (x) (1 + \sin (x))} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.10.2.3

Rewrite the expression.

$\frac{\sin^{2} (x)}{\cos^{2} (x)} - \frac{\sin^{2} (x)}{\cos^{2} (x)} = 0$

Step 2.11

Subtract $\frac{\sin^{2} (x)}{\cos^{2} (x)}$ from $\frac{\sin^{2} (x)}{\cos^{2} (x)}$ .

$0 = 0$

Step 3

The domain of the expression is all real numbers except where the expression is undefined. In this case, there is no real number that makes the expression undefined.