Trigonometry Examples

${(\tan (x) + \cot (x))}^{2} = \sec^{2} (x) + \csc^{2} (x)$

Step 1

Start on the left side.

${(\tan (x) + \cot (x))}^{2}$

Step 2

Simplify.

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Step 2.1

Rewrite ${(\tan (x) + \cot (x))}^{2}$ as $(\tan (x) + \cot (x)) (\tan (x) + \cot (x))$ .

$(\tan (x) + \cot (x)) (\tan (x) + \cot (x))$

Step 2.2

Expand $(\tan (x) + \cot (x)) (\tan (x) + \cot (x))$ using the FOIL Method.

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Step 2.2.1

Apply the distributive property.

$\tan (x) (\tan (x) + \cot (x)) + \cot (x) (\tan (x) + \cot (x))$

Step 2.2.2

Apply the distributive property.

$\tan (x) \tan (x) + \tan (x) \cot (x) + \cot (x) (\tan (x) + \cot (x))$

Step 2.2.3

Apply the distributive property.

$\tan (x) \tan (x) + \tan (x) \cot (x) + \cot (x) \tan (x) + \cot (x) \cot (x)$

Step 2.3

Simplify and combine like terms.

$\tan^{2} (x) + 2 \cot (x) \tan (x) + \cot^{2} (x)$

Step 3

Apply Pythagorean identity in reverse.

$\sec^{2} (x) - 1 + 2 \cot (x) \tan (x) + \cot^{2} (x)$

Step 4

Factor.

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Step 4.1

Rewrite $1$ as $1^{2}$ .

$\sec^{2} (x) - 1^{2} + 2 \cot (x) \tan (x) + \cot^{2} (x)$

Step 4.2

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = \sec (x)$ and $b = 1$ .

$(\sec (x) + 1) (\sec (x) - 1) + 2 \cot (x) \tan (x) + \cot^{2} (x)$

Step 5

Apply Pythagorean identity in reverse.

$(\sec (x) + 1) (\sec (x) - 1) + 2 \cot (x) \tan (x) + \csc^{2} (x) - 1$

Step 6

Convert to sines and cosines.

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Step 6.1

Apply the reciprocal identity to $\sec (x)$ .

$(\frac{1}{\cos (x)} + 1) (\sec (x) - 1) + 2 \cot (x) \tan (x) + \csc^{2} (x) - 1$

Step 6.2

Apply the reciprocal identity to $\sec (x)$ .

$(\frac{1}{\cos (x)} + 1) (\frac{1}{\cos (x)} - 1) + 2 \cot (x) \tan (x) + \csc^{2} (x) - 1$

Step 6.3

Write $\cot (x)$ in sines and cosines using the quotient identity.

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

Step 6.4

Write $\tan (x)$ in sines and cosines using the quotient identity.

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

Step 6.5

Apply the reciprocal identity to $\csc (x)$ .

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

Step 6.6

Apply the product rule to $\frac{1}{\sin (x)}$ .

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

Step 7

Simplify.

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Step 7.1

Simplify each term.

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Step 7.1.1

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

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Step 7.1.1.1

Apply the distributive property.

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

Step 7.1.1.2

Apply the distributive property.

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

Step 7.1.1.3

Apply the distributive property.

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

Step 7.1.2

Simplify and combine like terms.

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Step 7.1.2.1

Simplify each term.

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Step 7.1.2.1.1

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

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Step 7.1.2.1.1.1

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

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

Step 7.1.2.1.1.2

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

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

Step 7.1.2.1.1.3

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

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

Step 7.1.2.1.1.4

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

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

Step 7.1.2.1.1.5

Add $1$ and $1$ .

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

Step 7.1.2.1.2

Combine $\frac{1}{\cos (x)}$ and $- 1$ .

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

Step 7.1.2.1.3

Move the negative in front of the fraction.

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

Step 7.1.2.1.4

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

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

Step 7.1.2.1.5

Multiply $- 1$ by $1$ .

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

Step 7.1.2.2

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

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

Step 7.1.2.3

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

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Step 7.1.2.3.1

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

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

Step 7.1.2.3.2

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

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

Step 7.1.2.3.3

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

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

Step 7.1.2.3.4

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

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

Step 7.1.2.3.5

Add $1$ and $1$ .

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

Step 7.1.2.4

Combine the numerators over the common denominator.

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

Step 7.1.2.5

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

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

Step 7.1.2.6

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

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Step 7.1.2.6.1

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

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

Step 7.1.2.6.2

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

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

Step 7.1.2.6.3

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

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

Step 7.1.2.6.4

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

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

Step 7.1.2.6.5

Add $1$ and $1$ .

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

Step 7.1.2.7

Combine the numerators over the common denominator.

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

Step 7.1.2.8

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

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

Step 7.1.2.9

Combine $- 1$ and $\frac{{\cos (x)}^{2}}{{\cos (x)}^{2}}$ .

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

Step 7.1.2.10

Combine the numerators over the common denominator.

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

Step 7.1.3

Simplify the numerator.

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Step 7.1.3.1

Add $- \cos (x)$ and $\cos (x)$ .

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

Step 7.1.3.2

Add $1$ and $0$ .

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

Step 7.1.3.3

Rewrite $1$ as $1^{2}$ .

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

Step 7.1.3.4

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = 1$ and $b = \cos (x)$ .

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

Step 7.1.4

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

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

Step 7.1.5

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

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Step 7.1.5.1

Factor $\cos (x)$ out of $2 \cos (x)$ .

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

Step 7.1.5.2

Cancel the common factor.

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

Step 7.1.5.3

Rewrite the expression.

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

Step 7.1.6

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

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Step 7.1.6.1

Cancel the common factor.

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

Step 7.1.6.2

Rewrite the expression.

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

Step 7.1.7

One to any power is one.

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

Step 7.2

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

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

Step 7.3

Combine the numerators over the common denominator.

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

Step 7.4

Simplify the numerator.

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Step 7.4.1

Expand $(1 + \cos (x)) (1 - \cos (x))$ using the FOIL Method.

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Step 7.4.1.1

Apply the distributive property.

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

Step 7.4.1.2

Apply the distributive property.

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

Step 7.4.1.3

Apply the distributive property.

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

Step 7.4.2

Simplify and combine like terms.

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Step 7.4.2.1

Simplify each term.

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Step 7.4.2.1.1

Multiply $1$ by $1$ .

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

Step 7.4.2.1.2

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

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

Step 7.4.2.1.3

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

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

Step 7.4.2.1.4

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

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Step 7.4.2.1.4.1

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

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

Step 7.4.2.1.4.2

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

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

Step 7.4.2.1.4.3

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

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

Step 7.4.2.1.4.4

Add $1$ and $1$ .

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

Step 7.4.2.2

Add $- \cos (x)$ and $\cos (x)$ .

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

Step 7.4.2.3

Add $1$ and $0$ .

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

Step 7.4.3

Add $- {\cos (x)}^{2}$ and $2 {\cos (x)}^{2}$ .

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

Step 7.5

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

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

Step 7.6

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

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

Step 7.7

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

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Step 7.7.1

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

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

Step 7.7.2

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

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

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

Step 7.8

Combine the numerators over the common denominator.

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

Step 7.9

Simplify the numerator.

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Step 7.9.1

Apply the distributive property.

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

Step 7.9.2

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

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

Step 7.10

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

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

Step 7.11

Combine $- 1$ and $\frac{{\cos (x)}^{2} {\sin (x)}^{2}}{{\cos (x)}^{2} {\sin (x)}^{2}}$ .

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

Step 7.12

Combine the numerators over the common denominator.

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

Step 7.13

Simplify the numerator.

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

Step 8

Now consider the right side of the equation.

$\sec^{2} (x) + \csc^{2} (x)$

Step 9

Convert to sines and cosines.

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Step 9.1

Apply the reciprocal identity to $\sec (x)$ .

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

Step 9.2

Apply the reciprocal identity to $\csc (x)$ .

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

Step 9.3

Apply the product rule to $\frac{1}{\cos (x)}$ .

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

Step 9.4

Apply the product rule to $\frac{1}{\sin (x)}$ .

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

Step 10

Simplify each term.

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

Step 11

Add fractions.

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Step 11.1

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

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

Step 11.2

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

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

Step 11.3

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

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Step 11.3.1

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

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

Step 11.3.2

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

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

Step 11.3.3

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

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

Step 11.4

Combine the numerators over the common denominator.

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

Step 12

Because the two sides have been shown to be equivalent, the equation is an identity.

${(\tan (x) + \cot (x))}^{2} = \sec^{2} (x) + \csc^{2} (x)$ is an identity