Trigonometry Examples

$92 \cos (15)$

Step 1

The exact value of $\cos (15)$ is $\frac{\sqrt{6} + \sqrt{2}}{4}$ .

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Step 1.1

Split $15$ into two angles where the values of the six trigonometric functions are known.

$92 \cos (45 - 30)$

Step 1.2

Separate negation.

$92 \cos (45 - (30))$

Step 1.3

Apply the difference of angles identity $\cos (x - y) = \cos (x) \cos (y) + \sin (x) \sin (y)$ .

$92 (\cos (45) \cos (30) + \sin (45) \sin (30))$

Step 1.4

The exact value of $\cos (45)$ is $\frac{\sqrt{2}}{2}$ .

$92 (\frac{\sqrt{2}}{2} \cos (30) + \sin (45) \sin (30))$

Step 1.5

The exact value of $\cos (30)$ is $\frac{\sqrt{3}}{2}$ .

$92 (\frac{\sqrt{2}}{2} \cdot \frac{\sqrt{3}}{2} + \sin (45) \sin (30))$

Step 1.6

The exact value of $\sin (45)$ is $\frac{\sqrt{2}}{2}$ .

$92 (\frac{\sqrt{2}}{2} \cdot \frac{\sqrt{3}}{2} + \frac{\sqrt{2}}{2} \sin (30))$

Step 1.7

The exact value of $\sin (30)$ is $\frac{1}{2}$ .

$92 (\frac{\sqrt{2}}{2} \cdot \frac{\sqrt{3}}{2} + \frac{\sqrt{2}}{2} \cdot \frac{1}{2})$

Step 1.8

Simplify $\frac{\sqrt{2}}{2} \cdot \frac{\sqrt{3}}{2} + \frac{\sqrt{2}}{2} \cdot \frac{1}{2}$ .

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Step 1.8.1

Simplify each term.

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Step 1.8.1.1

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

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Step 1.8.1.1.1

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

$92 (\frac{\sqrt{2} \sqrt{3}}{2 \cdot 2} + \frac{\sqrt{2}}{2} \cdot \frac{1}{2})$

Step 1.8.1.1.2

Combine using the product rule for radicals.

$92 (\frac{\sqrt{2 \cdot 3}}{2 \cdot 2} + \frac{\sqrt{2}}{2} \cdot \frac{1}{2})$

Step 1.8.1.1.3

Multiply $2$ by $3$ .

$92 (\frac{\sqrt{6}}{2 \cdot 2} + \frac{\sqrt{2}}{2} \cdot \frac{1}{2})$

Step 1.8.1.1.4

Multiply $2$ by $2$ .

$92 (\frac{\sqrt{6}}{4} + \frac{\sqrt{2}}{2} \cdot \frac{1}{2})$

Step 1.8.1.2

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

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Step 1.8.1.2.1

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

$92 (\frac{\sqrt{6}}{4} + \frac{\sqrt{2}}{2 \cdot 2})$

Step 1.8.1.2.2

Multiply $2$ by $2$ .

$92 (\frac{\sqrt{6}}{4} + \frac{\sqrt{2}}{4})$

Step 1.8.2

Combine the numerators over the common denominator.

$92 \frac{\sqrt{6} + \sqrt{2}}{4}$

Step 2

Cancel the common factor of $4$ .

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Step 2.1

Factor $4$ out of $92$ .

$4 (23) \frac{\sqrt{6} + \sqrt{2}}{4}$

Step 2.2

Cancel the common factor.

$4 \cdot 23 \frac{\sqrt{6} + \sqrt{2}}{4}$

Step 2.3

Rewrite the expression.

$23 (\sqrt{6} + \sqrt{2})$

Step 3

Apply the distributive property.

$23 \sqrt{6} + 23 \sqrt{2}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$23 \sqrt{6} + 23 \sqrt{2}$

Decimal Form:

$88.86517601 \dots$