Precalculus Examples

$\sin (θ) = - \frac{3}{7}$

Step 1

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

$\sin (θ) = \frac{opposite}{hypotenuse}$

Step 2

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

$Adjacent = - \sqrt{{hypotenuse}^{2} - {opposite}^{2}}$

Step 3

Replace the known values in the equation.

$Adjacent = - \sqrt{{(7)}^{2} - {(- 3)}^{2}}$

Step 4

Simplify inside the radical.

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Step 4.1

Negate $\sqrt{{(7)}^{2} - {(- 3)}^{2}}$ .

Adjacent $= - \sqrt{{(7)}^{2} - {(- 3)}^{2}}$

Step 4.2

Raise $7$ to the power of $2$ .

Adjacent $= - \sqrt{49 - {(- 3)}^{2}}$

Step 4.3

Raise $- 3$ to the power of $2$ .

Adjacent $= - \sqrt{49 - 1 \cdot 9}$

Step 4.4

Multiply $- 1$ by $9$ .

Adjacent $= - \sqrt{49 - 9}$

Step 4.5

Subtract $9$ from $49$ .

Adjacent $= - \sqrt{40}$

Step 4.6

Rewrite $40$ as $2^{2} \cdot 10$ .

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Step 4.6.1

Factor $4$ out of $40$ .

Adjacent $= - \sqrt{4 (10)}$

Step 4.6.2

Rewrite $4$ as $2^{2}$ .

Adjacent $= - \sqrt{2^{2} \cdot 10}$

Step 4.7

Pull terms out from under the radical.

Adjacent $= - (2 \sqrt{10})$

Step 4.8

Multiply $2$ by $- 1$ .

Adjacent $= - 2 \sqrt{10}$

Step 5

Find the value of cosine.

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Step 5.1

Use the definition of cosine to find the value of $\cos (θ)$ .

$\cos (θ) = \frac{adj}{hyp}$

Step 5.2

Substitute in the known values.

$\cos (θ) = \frac{- 2 \sqrt{10}}{7}$

Step 5.3

Move the negative in front of the fraction.

$\cos (θ) = - \frac{2 \sqrt{10}}{7}$

Step 6

Find the value of tangent.

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Step 6.1

Use the definition of tangent to find the value of $\tan (θ)$ .

$\tan (θ) = \frac{opp}{adj}$

Step 6.2

Substitute in the known values.

$\tan (θ) = \frac{- 3}{- 2 \sqrt{10}}$

Step 6.3

Simplify the value of $\tan (θ)$ .

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Step 6.3.1

Dividing two negative values results in a positive value.

$\tan (θ) = \frac{3}{(2) \sqrt{10}}$

Step 6.3.2

Multiply $\frac{3}{2 \sqrt{10}}$ by $\frac{\sqrt{10}}{\sqrt{10}}$ .

$\tan (θ) = \frac{3}{2 \sqrt{10}} \cdot \frac{\sqrt{10}}{\sqrt{10}}$

Step 6.3.3

Combine and simplify the denominator.

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Step 6.3.3.1

Multiply $\frac{3}{2 \sqrt{10}}$ by $\frac{\sqrt{10}}{\sqrt{10}}$ .

$\tan (θ) = \frac{3 \sqrt{10}}{2 \sqrt{10} \sqrt{10}}$

Step 6.3.3.2

Move $\sqrt{10}$ .

$\tan (θ) = \frac{3 \sqrt{10}}{2 (\sqrt{10} \sqrt{10})}$

Step 6.3.3.3

Raise $\sqrt{10}$ to the power of $1$ .

$\tan (θ) = \frac{3 \sqrt{10}}{2 (\sqrt{10} \sqrt{10})}$

Step 6.3.3.4

Raise $\sqrt{10}$ to the power of $1$ .

$\tan (θ) = \frac{3 \sqrt{10}}{2 (\sqrt{10} \sqrt{10})}$

Step 6.3.3.5

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

$\tan (θ) = \frac{3 \sqrt{10}}{2 {\sqrt{10}}^{1 + 1}}$

Step 6.3.3.6

Add $1$ and $1$ .

$\tan (θ) = \frac{3 \sqrt{10}}{2 {\sqrt{10}}^{2}}$

Step 6.3.3.7

Rewrite ${\sqrt{10}}^{2}$ as $10$ .

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Step 6.3.3.7.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{10}$ as $10^{\frac{1}{2}}$ .

$\tan (θ) = \frac{3 \sqrt{10}}{2 {(10^{\frac{1}{2}})}^{2}}$

Step 6.3.3.7.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\tan (θ) = \frac{3 \sqrt{10}}{2 \cdot 10^{\frac{1}{2} \cdot 2}}$

Step 6.3.3.7.3

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

$\tan (θ) = \frac{3 \sqrt{10}}{2 \cdot 10^{\frac{2}{2}}}$

Step 6.3.3.7.4

Cancel the common factor of $2$ .

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Step 6.3.3.7.4.1

Cancel the common factor.

$\tan (θ) = \frac{3 \sqrt{10}}{2 \cdot 10^{\frac{2}{2}}}$

Step 6.3.3.7.4.2

Rewrite the expression.

$\tan (θ) = \frac{3 \sqrt{10}}{2 \cdot 10}$

Step 6.3.3.7.5

Evaluate the exponent.

$\tan (θ) = \frac{3 \sqrt{10}}{2 \cdot 10}$

Step 6.3.4

Multiply $2$ by $10$ .

$\tan (θ) = \frac{3 \sqrt{10}}{20}$

Step 7

Find the value of cotangent.

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Step 7.1

Use the definition of cotangent to find the value of $\cot (θ)$ .

$\cot (θ) = \frac{adj}{opp}$

Step 7.2

Substitute in the known values.

$\cot (θ) = \frac{- 2 \sqrt{10}}{- 3}$

Step 7.3

Dividing two negative values results in a positive value.

$\cot (θ) = \frac{2 \sqrt{10}}{3}$

Step 8

Find the value of secant.

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Step 8.1

Use the definition of secant to find the value of $\sec (θ)$ .

$\sec (θ) = \frac{hyp}{adj}$

Step 8.2

Substitute in the known values.

$\sec (θ) = \frac{7}{- 2 \sqrt{10}}$

Step 8.3

Simplify the value of $\sec (θ)$ .

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Step 8.3.1

Move the negative in front of the fraction.

$\sec (θ) = - \frac{7}{(2) \sqrt{10}}$

Step 8.3.2

Multiply $\frac{7}{2 \sqrt{10}}$ by $\frac{\sqrt{10}}{\sqrt{10}}$ .

$\sec (θ) = - (\frac{7}{2 \sqrt{10}} \cdot \frac{\sqrt{10}}{\sqrt{10}})$

Step 8.3.3

Combine and simplify the denominator.

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Step 8.3.3.1

Multiply $\frac{7}{2 \sqrt{10}}$ by $\frac{\sqrt{10}}{\sqrt{10}}$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{2 \sqrt{10} \sqrt{10}}$

Step 8.3.3.2

Move $\sqrt{10}$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{2 (\sqrt{10} \sqrt{10})}$

Step 8.3.3.3

Raise $\sqrt{10}$ to the power of $1$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{2 (\sqrt{10} \sqrt{10})}$

Step 8.3.3.4

Raise $\sqrt{10}$ to the power of $1$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{2 (\sqrt{10} \sqrt{10})}$

Step 8.3.3.5

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

$\sec (θ) = - \frac{7 \sqrt{10}}{2 {\sqrt{10}}^{1 + 1}}$

Step 8.3.3.6

Add $1$ and $1$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{2 {\sqrt{10}}^{2}}$

Step 8.3.3.7

Rewrite ${\sqrt{10}}^{2}$ as $10$ .

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Step 8.3.3.7.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{10}$ as $10^{\frac{1}{2}}$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{2 {(10^{\frac{1}{2}})}^{2}}$

Step 8.3.3.7.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{2 \cdot 10^{\frac{1}{2} \cdot 2}}$

Step 8.3.3.7.3

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

$\sec (θ) = - \frac{7 \sqrt{10}}{2 \cdot 10^{\frac{2}{2}}}$

Step 8.3.3.7.4

Cancel the common factor of $2$ .

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Step 8.3.3.7.4.1

Cancel the common factor.

$\sec (θ) = - \frac{7 \sqrt{10}}{2 \cdot 10^{\frac{2}{2}}}$

Step 8.3.3.7.4.2

Rewrite the expression.

$\sec (θ) = - \frac{7 \sqrt{10}}{2 \cdot 10}$

Step 8.3.3.7.5

Evaluate the exponent.

$\sec (θ) = - \frac{7 \sqrt{10}}{2 \cdot 10}$

Step 8.3.4

Multiply $2$ by $10$ .

$\sec (θ) = - \frac{7 \sqrt{10}}{20}$

Step 9

Find the value of cosecant.

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Step 9.1

Use the definition of cosecant to find the value of $\csc (θ)$ .

$\csc (θ) = \frac{hyp}{opp}$

Step 9.2

Substitute in the known values.

$\csc (θ) = \frac{7}{- 3}$

Step 9.3

Move the negative in front of the fraction.

$\csc (θ) = - \frac{7}{3}$

Step 10

This is the solution to each trig value.

$\sin (θ) = - \frac{3}{7}$

$\cos (θ) = - \frac{2 \sqrt{10}}{7}$

$\tan (θ) = \frac{3 \sqrt{10}}{20}$

$\cot (θ) = \frac{2 \sqrt{10}}{3}$

$\sec (θ) = - \frac{7 \sqrt{10}}{20}$

$\csc (θ) = - \frac{7}{3}$