Trigonometry Examples

 $\begin{matrix} Side & Angle \\ \begin{matrix} b = & 4 \\ c = & 5 \\ a = & 3 \end{matrix} & \begin{matrix} A = \\ B = \\ C = \end{matrix} \end{matrix}$

Step 1

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 2

Replace the known values in the equation.

$Opposite = \sqrt{{(5)}^{2} - {(4)}^{2}}$

Step 3

Simplify inside the radical.

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Step 3.1

Raise $5$ to the power of $2$ .

Opposite $= \sqrt{25 - {(4)}^{2}}$

Step 3.2

Raise $4$ to the power of $2$ .

Opposite $= \sqrt{25 - 1 \cdot 16}$

Step 3.3

Multiply $- 1$ by $16$ .

Opposite $= \sqrt{25 - 16}$

Step 3.4

Subtract $16$ from $25$ .

Opposite $= \sqrt{9}$

Step 3.5

Rewrite $9$ as $3^{2}$ .

Opposite $= \sqrt{3^{2}}$

Step 3.6

Pull terms out from under the radical, assuming positive real numbers.

Opposite $= 3$

Step 4

Find the value of cosine.

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Step 4.1

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

$\frac{adjacent}{hypotenuse}$

Step 4.2

Substitute in the known values.

$\cos (A) \cos (A) = \frac{4}{5}$

Step 5

Find the value of sine.

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Step 5.1

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

$\sin (A) = \frac{opp}{hyp}$

Step 5.2

Substitute in the known values.

$\sin (A) = \frac{3}{5}$

Step 6

Find the value of tangent.

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Step 6.1

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

$\tan (A) = \frac{opp}{adj}$

Step 6.2

Substitute in the known values.

$\tan (A) = \frac{3}{4}$

Step 7

Find the value of cotangent.

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Step 7.1

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

$\cot (A) = \frac{adj}{opp}$

Step 7.2

Substitute in the known values.

$\cot (A) = \frac{4}{3}$

Step 8

Find the value of secant.

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Step 8.1

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

$\sec (A) = \frac{hyp}{adj}$

Step 8.2

Substitute in the known values.

$\sec (A) = \frac{5}{4}$

Step 9

Find the value of cosecant.

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Step 9.1

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

$\csc (A) = \frac{hyp}{opp}$

Step 9.2

Substitute in the known values.

$\csc (A) = \frac{5}{3}$

Step 10

This is the solution to each trig value.

$\sin (A) = \frac{3}{5}$

$\cos (A) = \frac{4}{5}$

$\tan (A) = \frac{3}{4}$

$\cot (A) = \frac{4}{3}$

$\sec (A) = \frac{5}{4}$

$\csc (A) = \frac{5}{3}$