Trigonometry Examples

$\cos (60 ° - 45 °)$

Step 1

Use the difference formula for cosine to simplify the expression. The formula states that $\cos (A - B) = \cos (A) \cos (B) + \sin (A) \sin (B)$ .

$\cos (60 °) \cdot \cos (45 °) + \sin (60 °) \cdot \sin (45 °)$

Step 2

Remove parentheses.

$\cos (60 °) \cdot \cos (45 °) + \sin (60 °) \cdot \sin (45 °)$

Step 3

Simplify each term.

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Step 3.1

The exact value of $\cos (60 °)$ is $\frac{1}{2}$ .

$\frac{1}{2} \cdot \cos (45 °) + \sin (60 °) \cdot \sin (45 °)$

Step 3.2

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

$\frac{1}{2} \cdot \frac{\sqrt{2}}{2} + \sin (60 °) \cdot \sin (45 °)$

Step 3.3

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

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Step 3.3.1

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

$\frac{\sqrt{2}}{2 \cdot 2} + \sin (60 °) \cdot \sin (45 °)$

Step 3.3.2

Multiply $2$ by $2$ .

$\frac{\sqrt{2}}{4} + \sin (60 °) \cdot \sin (45 °)$

Step 3.4

The exact value of $\sin (60 °)$ is $\frac{\sqrt{3}}{2}$ .

$\frac{\sqrt{2}}{4} + \frac{\sqrt{3}}{2} \cdot \sin (45 °)$

Step 3.5

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

$\frac{\sqrt{2}}{4} + \frac{\sqrt{3}}{2} \cdot \frac{\sqrt{2}}{2}$

Step 3.6

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

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Step 3.6.1

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

$\frac{\sqrt{2}}{4} + \frac{\sqrt{3} \sqrt{2}}{2 \cdot 2}$

Step 3.6.2

Combine using the product rule for radicals.

$\frac{\sqrt{2}}{4} + \frac{\sqrt{3 \cdot 2}}{2 \cdot 2}$

Step 3.6.3

Multiply $3$ by $2$ .

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

Step 3.6.4

Multiply $2$ by $2$ .

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

Step 4

Combine the numerators over the common denominator.

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

Step 5

The result can be shown in multiple forms.

Exact Form:

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

Decimal Form:

$0.96592582 \dots$