Precalculus Examples

cos (θ) = \frac{4}{7}

$\cos (θ) = \frac{4}{7}$ ,

$\csc (θ) < 0$

Step 1

The cosecant function is negative in the third and fourth quadrants. The cosine function is positive in the first and fourth quadrants. The set of solutions for

$θ$ are limited to the fourth quadrant since that is the only quadrant found in both sets.

Solution is in the fourth quadrant.

Step 2

Use the definition of cosine to find the known sides of the unit circle right triangle. The quadrant determines the sign on each of the values.

$\cos (θ) = \frac{adjacent}{hypotenuse}$

Step 3

Find the opposite side of the unit circle triangle. Since the adjacent side and hypotenuse are known, use the Pythagorean theorem to find the remaining side.

$Opposite = - \sqrt{{hypotenuse}^{2} - {adjacent}^{2}}$

Step 4

Replace the known values in the equation.

$Opposite = - \sqrt{{(7)}^{2} - {(4)}^{2}}$

Step 5

Simplify inside the radical.

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Step 5.1

Negate

$\sqrt{{(7)}^{2} - {(4)}^{2}}$ .

Opposite

$= - \sqrt{{(7)}^{2} - {(4)}^{2}}$

Step 5.2

Raise

$7$ to the power of

$2$ .

Opposite

$= - \sqrt{49 - {(4)}^{2}}$

Step 5.3

Raise

$4$ to the power of

$2$ .

Opposite

$= - \sqrt{49 - 1 \cdot 16}$

Step 5.4

Multiply

$- 1$ by

$16$ .

Opposite

$= - \sqrt{49 - 16}$

Step 5.5

Subtract

$16$ from

$49$ .

Opposite

$= - \sqrt{33}$

Opposite

$= - \sqrt{33}$

Step 6

Find the value of sine.

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Step 6.1

Use the definition of sine to find the value of

$\sin (θ)$ .

$\sin (θ) = \frac{opp}{hyp}$

Step 6.2

Substitute in the known values.

$\sin (θ) = \frac{- \sqrt{33}}{7}$

Step 6.3

Move the negative in front of the fraction.

$\sin (θ) = - \frac{\sqrt{33}}{7}$

Step 7

Find the value of tangent.

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Step 7.1

Use the definition of tangent to find the value of

$\tan (θ)$ .

$\tan (θ) = \frac{opp}{adj}$

Step 7.2

Substitute in the known values.

$\tan (θ) = \frac{- \sqrt{33}}{4}$

Step 7.3

Move the negative in front of the fraction.

$\tan (θ) = - \frac{\sqrt{33}}{4}$

Step 8

Find the value of cotangent.

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Step 8.1

Use the definition of cotangent to find the value of

$\cot (θ)$ .

$\cot (θ) = \frac{adj}{opp}$

Step 8.2

Substitute in the known values.

$\cot (θ) = \frac{4}{- \sqrt{33}}$

Step 8.3

Simplify the value of

$\cot (θ)$ .

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Step 8.3.1

Move the negative in front of the fraction.

$\cot (θ) = - \frac{4}{\sqrt{33}}$

Step 8.3.2

Multiply

$\frac{4}{\sqrt{33}}$ by

$\frac{\sqrt{33}}{\sqrt{33}}$ .

$\cot (θ) = - (\frac{4}{\sqrt{33}} \cdot \frac{\sqrt{33}}{\sqrt{33}})$

Step 8.3.3

Combine and simplify the denominator.

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Step 8.3.3.1

Multiply

$\frac{4}{\sqrt{33}}$ by

$\frac{\sqrt{33}}{\sqrt{33}}$ .

$\cot (θ) = - \frac{4 \sqrt{33}}{\sqrt{33} \sqrt{33}}$

Step 8.3.3.2

Raise

$\sqrt{33}$ to the power of

$1$ .

$\cot (θ) = - \frac{4 \sqrt{33}}{\sqrt{33} \sqrt{33}}$

Step 8.3.3.3

Raise

$\sqrt{33}$ to the power of

$1$ .

$\cot (θ) = - \frac{4 \sqrt{33}}{\sqrt{33} \sqrt{33}}$

Step 8.3.3.4

Use the power rule

$a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\cot (θ) = - \frac{4 \sqrt{33}}{{\sqrt{33}}^{1 + 1}}$

Step 8.3.3.5

Add

$1$ and

$1$ .

$\cot (θ) = - \frac{4 \sqrt{33}}{{\sqrt{33}}^{2}}$

Step 8.3.3.6

Rewrite

${\sqrt{33}}^{2}$ as

$33$ .

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Step 8.3.3.6.1

Use

$\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite

$\sqrt{33}$ as

$33^{\frac{1}{2}}$ .

$\cot (θ) = - \frac{4 \sqrt{33}}{{(33^{\frac{1}{2}})}^{2}}$

Step 8.3.3.6.2

Apply the power rule and multiply exponents,

${(a^{m})}^{n} = a^{m n}$ .

$\cot (θ) = - \frac{4 \sqrt{33}}{33^{\frac{1}{2} \cdot 2}}$

Step 8.3.3.6.3

Combine

$\frac{1}{2}$ and

$2$ .

$\cot (θ) = - \frac{4 \sqrt{33}}{33^{\frac{2}{2}}}$

Step 8.3.3.6.4

Cancel the common factor of

$2$ .

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Step 8.3.3.6.4.1

Cancel the common factor.

$\cot (θ) = - \frac{4 \sqrt{33}}{33^{\frac{2}{2}}}$

Step 8.3.3.6.4.2

Rewrite the expression.

$\cot (θ) = - \frac{4 \sqrt{33}}{33}$

Step 8.3.3.6.5

Evaluate the exponent.

$\cot (θ) = - \frac{4 \sqrt{33}}{33}$

Step 9

Find the value of secant.

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Step 9.1

Use the definition of secant to find the value of

$\sec (θ)$ .

$\sec (θ) = \frac{hyp}{adj}$

Step 9.2

Substitute in the known values.

$\sec (θ) = \frac{7}{4}$

Step 10

Find the value of cosecant.

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Step 10.1

Use the definition of cosecant to find the value of

$\csc (θ)$ .

$\csc (θ) = \frac{hyp}{opp}$

Step 10.2

Substitute in the known values.

$\csc (θ) = \frac{7}{- \sqrt{33}}$

Step 10.3

Simplify the value of

$\csc (θ)$ .

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Step 10.3.1

Move the negative in front of the fraction.

$\csc (θ) = - \frac{7}{\sqrt{33}}$

Step 10.3.2

Multiply

$\frac{7}{\sqrt{33}}$ by

$\frac{\sqrt{33}}{\sqrt{33}}$ .

$\csc (θ) = - (\frac{7}{\sqrt{33}} \cdot \frac{\sqrt{33}}{\sqrt{33}})$

Step 10.3.3

Combine and simplify the denominator.

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Step 10.3.3.1

Multiply

$\frac{7}{\sqrt{33}}$ by

$\frac{\sqrt{33}}{\sqrt{33}}$ .

$\csc (θ) = - \frac{7 \sqrt{33}}{\sqrt{33} \sqrt{33}}$

Step 10.3.3.2

Raise

$\sqrt{33}$ to the power of

$1$ .

$\csc (θ) = - \frac{7 \sqrt{33}}{\sqrt{33} \sqrt{33}}$

Step 10.3.3.3

Raise

$\sqrt{33}$ to the power of

$1$ .

$\csc (θ) = - \frac{7 \sqrt{33}}{\sqrt{33} \sqrt{33}}$

Step 10.3.3.4

Use the power rule

$a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\csc (θ) = - \frac{7 \sqrt{33}}{{\sqrt{33}}^{1 + 1}}$

Step 10.3.3.5

Add

$1$ and

$1$ .

$\csc (θ) = - \frac{7 \sqrt{33}}{{\sqrt{33}}^{2}}$

Step 10.3.3.6

Rewrite

${\sqrt{33}}^{2}$ as

$33$ .

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Step 10.3.3.6.1

Use

$\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite

$\sqrt{33}$ as

$33^{\frac{1}{2}}$ .

$\csc (θ) = - \frac{7 \sqrt{33}}{{(33^{\frac{1}{2}})}^{2}}$

Step 10.3.3.6.2

Apply the power rule and multiply exponents,

${(a^{m})}^{n} = a^{m n}$ .

$\csc (θ) = - \frac{7 \sqrt{33}}{33^{\frac{1}{2} \cdot 2}}$

Step 10.3.3.6.3

Combine

$\frac{1}{2}$ and

$2$ .

$\csc (θ) = - \frac{7 \sqrt{33}}{33^{\frac{2}{2}}}$

Step 10.3.3.6.4

Cancel the common factor of

$2$ .

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Step 10.3.3.6.4.1

Cancel the common factor.

$\csc (θ) = - \frac{7 \sqrt{33}}{33^{\frac{2}{2}}}$

Step 10.3.3.6.4.2

Rewrite the expression.

$\csc (θ) = - \frac{7 \sqrt{33}}{33}$

Step 10.3.3.6.5

Evaluate the exponent.

$\csc (θ) = - \frac{7 \sqrt{33}}{33}$

Step 11

This is the solution to each trig value.

$\sin (θ) = - \frac{\sqrt{33}}{7}$

$\cos (θ) = \frac{4}{7}$

$\tan (θ) = - \frac{\sqrt{33}}{4}$

$\cot (θ) = - \frac{4 \sqrt{33}}{33}$

$\sec (θ) = \frac{7}{4}$

$\csc (θ) = - \frac{7 \sqrt{33}}{33}$