Trigonometry Examples

$\frac{\cos (a)}{1 - \tan (a)} + \frac{\sin (a)}{1 - \cot (a)}$

Step 1

Simplify each term.

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Step 1.1

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

$\frac{\cos (a)}{1 - \frac{\sin (a)}{\cos (a)}} + \frac{\sin (a)}{1 - \cot (a)}$

Step 1.2

Rewrite $\cot (a)$ in terms of sines and cosines.

$\frac{\cos (a)}{1 - \frac{\sin (a)}{\cos (a)}} + \frac{\sin (a)}{1 - \frac{\cos (a)}{\sin (a)}}$

Step 2

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

$\frac{\cos (a)}{1 - \frac{\sin (a)}{\cos (a)}} \cdot \frac{1 - \frac{\cos (a)}{\sin (a)}}{1 - \frac{\cos (a)}{\sin (a)}} + \frac{\sin (a)}{1 - \frac{\cos (a)}{\sin (a)}}$

Step 3

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

$\frac{\cos (a)}{1 - \frac{\sin (a)}{\cos (a)}} \cdot \frac{1 - \frac{\cos (a)}{\sin (a)}}{1 - \frac{\cos (a)}{\sin (a)}} + \frac{\sin (a)}{1 - \frac{\cos (a)}{\sin (a)}} \cdot \frac{1 - \frac{\sin (a)}{\cos (a)}}{1 - \frac{\sin (a)}{\cos (a)}}$

Step 4

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

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Step 4.1

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

$\frac{\cos (a) (1 - \frac{\cos (a)}{\sin (a)})}{(1 - \frac{\sin (a)}{\cos (a)}) (1 - \frac{\cos (a)}{\sin (a)})} + \frac{\sin (a)}{1 - \frac{\cos (a)}{\sin (a)}} \cdot \frac{1 - \frac{\sin (a)}{\cos (a)}}{1 - \frac{\sin (a)}{\cos (a)}}$

Step 4.2

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

$\frac{\cos (a) (1 - \frac{\cos (a)}{\sin (a)})}{(1 - \frac{\sin (a)}{\cos (a)}) (1 - \frac{\cos (a)}{\sin (a)})} + \frac{\sin (a) (1 - \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 4.3

Reorder the factors of $(1 - \frac{\sin (a)}{\cos (a)}) (1 - \frac{\cos (a)}{\sin (a)})$ .

$\frac{\cos (a) (1 - \frac{\cos (a)}{\sin (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})} + \frac{\sin (a) (1 - \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 5

Combine the numerators over the common denominator.

$\frac{\cos (a) (1 - \frac{\cos (a)}{\sin (a)}) + \sin (a) (1 - \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 6

Simplify the numerator.

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Step 6.1

Apply the distributive property.

$\frac{\cos (a) \cdot 1 + \cos (a) (- \frac{\cos (a)}{\sin (a)}) + \sin (a) (1 - \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 6.2

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

$\frac{\cos (a) + \cos (a) (- \frac{\cos (a)}{\sin (a)}) + \sin (a) (1 - \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 6.3

Rewrite using the commutative property of multiplication.

$\frac{\cos (a) - \cos (a) \frac{\cos (a)}{\sin (a)} + \sin (a) (1 - \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 6.4

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

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Step 6.4.1

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

$\frac{\cos (a) - \frac{\cos (a) \cos (a)}{\sin (a)} + \sin (a) (1 - \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 6.4.2

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

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

Step 6.4.3

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

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

Step 6.4.4

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

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

Step 6.4.5

Add $1$ and $1$ .

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

Step 6.5

Apply the distributive property.

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

Step 6.6

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

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

Step 6.7

Rewrite using the commutative property of multiplication.

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

Step 6.8

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

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Step 6.8.1

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

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

Step 6.8.2

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

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

Step 6.8.3

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

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

Step 6.8.4

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

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

Step 6.8.5

Add $1$ and $1$ .

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

Step 7

Simplify the numerator.

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Step 7.1

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

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

Step 7.2

Separate fractions.

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

Step 7.3

Convert from $\frac{\cos (a)}{\sin (a)}$ to $\cot (a)$ .

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

Step 7.4

Divide $\cos (a)$ by $1$ .

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

Step 7.5

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

$\frac{\cos (a) - \cos (a) \cot (a) + \sin (a) - \frac{\sin (a) \sin (a)}{\cos (a)}}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 7.6

Separate fractions.

$\frac{\cos (a) - \cos (a) \cot (a) + \sin (a) - (\frac{\sin (a)}{1} \cdot \frac{\sin (a)}{\cos (a)})}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 7.7

Convert from $\frac{\sin (a)}{\cos (a)}$ to $\tan (a)$ .

$\frac{\cos (a) - \cos (a) \cot (a) + \sin (a) - (\frac{\sin (a)}{1} \tan (a))}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 7.8

Divide $\sin (a)$ by $1$ .

$\frac{\cos (a) - \cos (a) \cot (a) + \sin (a) - \sin (a) \tan (a)}{(1 - \frac{\cos (a)}{\sin (a)}) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 8

Simplify the denominator.

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Step 8.1

Convert from $\frac{\cos (a)}{\sin (a)}$ to $\cot (a)$ .

$\frac{\cos (a) - \cos (a) \cot (a) + \sin (a) - \sin (a) \tan (a)}{(1 - \cot (a)) (1 - \frac{\sin (a)}{\cos (a)})}$

Step 8.2

Convert from $\frac{\sin (a)}{\cos (a)}$ to $\tan (a)$ .

$\frac{\cos (a) - \cos (a) \cot (a) + \sin (a) - \sin (a) \tan (a)}{(1 - \cot (a)) (1 - \tan (a))}$