Trigonometry Examples

$\cos (θ) = - \frac{\sqrt{8}}{3}$

Step 1

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 2

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 3

Replace the known values in the equation.

$Opposite = - \sqrt{{(3)}^{2} - {(- \sqrt{8})}^{2}}$

Step 4

Simplify inside the radical.

Tap for more steps...

Step 4.1

Negate $\sqrt{{(3)}^{2} - {(- \sqrt{8})}^{2}}$ .

Opposite $= - \sqrt{{(3)}^{2} - {(- \sqrt{8})}^{2}}$

Step 4.2

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

Opposite $= - \sqrt{9 - {(- \sqrt{8})}^{2}}$

Step 4.3

Rewrite $8$ as $2^{2} \cdot 2$ .

Tap for more steps...

Step 4.3.1

Factor $4$ out of $8$ .

Opposite $= - \sqrt{9 - {(- \sqrt{4 (2)})}^{2}}$

Step 4.3.2

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

Opposite $= - \sqrt{9 - {(- \sqrt{2^{2} \cdot 2})}^{2}}$

Step 4.4

Pull terms out from under the radical.

Opposite $= - \sqrt{9 - {(- (2 \sqrt{2}))}^{2}}$

Step 4.5

Multiply $2$ by $- 1$ .

Opposite $= - \sqrt{9 - {(- 2 \sqrt{2})}^{2}}$

Step 4.6

Apply the product rule to $- 2 \sqrt{2}$ .

Opposite $= - \sqrt{9 - ({(- 2)}^{2} {\sqrt{2}}^{2})}$

Step 4.7

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

Opposite $= - \sqrt{9 - (4 {\sqrt{2}}^{2})}$

Step 4.8

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

Tap for more steps...

Step 4.8.1

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

Opposite $= - \sqrt{9 - (4 {(2^{\frac{1}{2}})}^{2})}$

Step 4.8.2

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

Opposite $= - \sqrt{9 - (4 \cdot 2^{\frac{1}{2} \cdot 2})}$

Step 4.8.3

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

Opposite $= - \sqrt{9 - (4 \cdot 2^{\frac{2}{2}})}$

Step 4.8.4

Cancel the common factor of $2$ .

Tap for more steps...

Step 4.8.4.1

Cancel the common factor.

Opposite $= - \sqrt{9 - (4 \cdot 2^{\frac{2}{2}})}$

Step 4.8.4.2

Rewrite the expression.

Opposite $= - \sqrt{9 - (4 \cdot 2)}$

Step 4.8.5

Evaluate the exponent.

Opposite $= - \sqrt{9 - (4 \cdot 2)}$

Step 4.9

Multiply $- (4 \cdot 2)$ .

Tap for more steps...

Step 4.9.1

Multiply $4$ by $2$ .

Opposite $= - \sqrt{9 - 1 \cdot 8}$

Step 4.9.2

Multiply $- 1$ by $8$ .

Opposite $= - \sqrt{9 - 8}$

Step 4.10

Subtract $8$ from $9$ .

Opposite $= - \sqrt{1}$

Step 4.11

Any root of $1$ is $1$ .

Opposite $= - 1 \cdot 1$

Step 4.12

Multiply $- 1$ by $1$ .

Opposite $= - 1$

Step 5

Find the value of sine.

Tap for more steps...

Step 5.1

Use the definition of sine to find the value of $\sin (θ)$ .

$\sin (θ) = \frac{opp}{hyp}$

Step 5.2

Substitute in the known values.

$\sin (θ) = \frac{- 1}{3}$

Step 5.3

Move the negative in front of the fraction.

$\sin (θ) = - \frac{1}{3}$

Step 6

Simplify the numerator.

Tap for more steps...

Step 6.1

Rewrite $8$ as $2^{2} \cdot 2$ .

Tap for more steps...

Step 6.1.1

Factor $4$ out of $8$ .

$\cos (θ) = - \frac{\sqrt{4 (2)}}{3}$

Step 6.1.2

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

$\cos (θ) = - \frac{\sqrt{2^{2} \cdot 2}}{3}$

Step 6.2

Pull terms out from under the radical.

$\cos (θ) = - \frac{2 \sqrt{2}}{3}$

Step 7

Find the value of tangent.

Tap for more steps...

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.

$\tan (θ) = \frac{- 1}{- \sqrt{8}}$

Step 7.3

Simplify the value of $\tan (θ)$ .

Tap for more steps...

Step 7.3.1

Dividing two negative values results in a positive value.

$\tan (θ) = \frac{1}{\sqrt{8}}$

Step 7.3.2

Simplify the denominator.

Tap for more steps...

Step 7.3.2.1

Rewrite $8$ as $2^{2} \cdot 2$ .

Tap for more steps...

Step 7.3.2.1.1

Factor $4$ out of $8$ .

$\tan (θ) = \frac{1}{\sqrt{4 (2)}}$

Step 7.3.2.1.2

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

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

Step 7.3.2.2

Pull terms out from under the radical.

$\tan (θ) = \frac{1}{2 \sqrt{2}}$

Step 7.3.3

Multiply $\frac{1}{2 \sqrt{2}}$ by $\frac{\sqrt{2}}{\sqrt{2}}$ .

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

Step 7.3.4

Combine and simplify the denominator.

Tap for more steps...

Step 7.3.4.1

Multiply $\frac{1}{2 \sqrt{2}}$ by $\frac{\sqrt{2}}{\sqrt{2}}$ .

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

Step 7.3.4.2

Move $\sqrt{2}$ .

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

Step 7.3.4.3

Raise $\sqrt{2}$ to the power of $1$ .

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

Step 7.3.4.4

Raise $\sqrt{2}$ to the power of $1$ .

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

Step 7.3.4.5

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

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

Step 7.3.4.6

Add $1$ and $1$ .

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

Step 7.3.4.7

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

Tap for more steps...

Step 7.3.4.7.1

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

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

Step 7.3.4.7.2

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

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

Step 7.3.4.7.3

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

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

Step 7.3.4.7.4

Cancel the common factor of $2$ .

Tap for more steps...

Step 7.3.4.7.4.1

Cancel the common factor.

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

Step 7.3.4.7.4.2

Rewrite the expression.

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

Step 7.3.4.7.5

Evaluate the exponent.

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

Step 7.3.5

Multiply $2$ by $2$ .

$\tan (θ) = \frac{\sqrt{2}}{4}$

Step 8

Find the value of cotangent.

Tap for more steps...

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.

$\cot (θ) = \frac{- \sqrt{8}}{- 1}$

Step 8.3

Simplify the value of $\cot (θ)$ .

Tap for more steps...

Step 8.3.1

Dividing two negative values results in a positive value.

$\cot (θ) = \frac{\sqrt{8}}{1}$

Step 8.3.2

Divide $\sqrt{8}$ by $1$ .

$\cot (θ) = \sqrt{8}$

Step 8.3.3

Rewrite $8$ as $2^{2} \cdot 2$ .

Tap for more steps...

Step 8.3.3.1

Factor $4$ out of $8$ .

$\cot (θ) = \sqrt{4 (2)}$

Step 8.3.3.2

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

$\cot (θ) = \sqrt{2^{2} \cdot 2}$

Step 8.3.4

Pull terms out from under the radical.

$\cot (θ) = 2 \sqrt{2}$

Step 9

Find the value of secant.

Tap for more steps...

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.

$\sec (θ) = \frac{3}{- \sqrt{8}}$

Step 9.3

Simplify the value of $\sec (θ)$ .

Tap for more steps...

Step 9.3.1

Simplify the denominator.

Tap for more steps...

Step 9.3.1.1

Rewrite $8$ as $2^{2} \cdot 2$ .

Tap for more steps...

Step 9.3.1.1.1

Factor $4$ out of $8$ .

$\sec (θ) = \frac{3}{- \sqrt{4 (2)}}$

Step 9.3.1.1.2

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

$\sec (θ) = \frac{3}{- \sqrt{2^{2} \cdot 2}}$

Step 9.3.1.2

Pull terms out from under the radical.

$\sec (θ) = \frac{3}{- 1 \cdot (2 \sqrt{2})}$

Step 9.3.1.3

Multiply $- 1$ by $2$ .

$\sec (θ) = \frac{3}{- 2 \sqrt{2}}$

Step 9.3.2

Move the negative in front of the fraction.

$\sec (θ) = - \frac{3}{2 \sqrt{2}}$

Step 9.3.3

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

$\sec (θ) = - (\frac{3}{2 \sqrt{2}} \cdot \frac{\sqrt{2}}{\sqrt{2}})$

Step 9.3.4

Combine and simplify the denominator.

Tap for more steps...

Step 9.3.4.1

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

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

Step 9.3.4.2

Move $\sqrt{2}$ .

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

Step 9.3.4.3

Raise $\sqrt{2}$ to the power of $1$ .

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

Step 9.3.4.4

Raise $\sqrt{2}$ to the power of $1$ .

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

Step 9.3.4.5

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

$\sec (θ) = - \frac{3 \sqrt{2}}{2 {\sqrt{2}}^{1 + 1}}$

Step 9.3.4.6

Add $1$ and $1$ .

$\sec (θ) = - \frac{3 \sqrt{2}}{2 {\sqrt{2}}^{2}}$

Step 9.3.4.7

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

Tap for more steps...

Step 9.3.4.7.1

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

$\sec (θ) = - \frac{3 \sqrt{2}}{2 {(2^{\frac{1}{2}})}^{2}}$

Step 9.3.4.7.2

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

$\sec (θ) = - \frac{3 \sqrt{2}}{2 \cdot 2^{\frac{1}{2} \cdot 2}}$

Step 9.3.4.7.3

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

$\sec (θ) = - \frac{3 \sqrt{2}}{2 \cdot 2^{\frac{2}{2}}}$

Step 9.3.4.7.4

Cancel the common factor of $2$ .

Tap for more steps...

Step 9.3.4.7.4.1

Cancel the common factor.

$\sec (θ) = - \frac{3 \sqrt{2}}{2 \cdot 2^{\frac{2}{2}}}$

Step 9.3.4.7.4.2

Rewrite the expression.

$\sec (θ) = - \frac{3 \sqrt{2}}{2 \cdot 2}$

Step 9.3.4.7.5

Evaluate the exponent.

$\sec (θ) = - \frac{3 \sqrt{2}}{2 \cdot 2}$

Step 9.3.5

Multiply $2$ by $2$ .

$\sec (θ) = - \frac{3 \sqrt{2}}{4}$

Step 10

Find the value of cosecant.

Tap for more steps...

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.

$\csc (θ) = \frac{3}{- 1}$

Step 10.3

Divide $3$ by $- 1$ .

$\csc (θ) = - 3$

Step 11

This is the solution to each trig value.

$\sin (θ) = - \frac{1}{3}$

$\cos (θ) = - \frac{2 \sqrt{2}}{3}$

$\tan (θ) = \frac{\sqrt{2}}{4}$

$\cot (θ) = 2 \sqrt{2}$

$\sec (θ) = - \frac{3 \sqrt{2}}{4}$

$\csc (θ) = - 3$