Trigonometry Examples

$\cos (\frac{v (24)}{7}) \cos (\frac{- \sqrt{45}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1

Simplify each term.

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Step 1.1

Move $24$ to the left of $v$ .

$\cos (\frac{24 v}{7}) \cos (\frac{- \sqrt{45}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1.2

Simplify the numerator.

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Step 1.2.1

Rewrite $45$ as $3^{2} \cdot 5$ .

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Step 1.2.1.1

Factor $9$ out of $45$ .

$\cos (\frac{24 v}{7}) \cos (\frac{- \sqrt{9 (5)}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1.2.1.2

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

$\cos (\frac{24 v}{7}) \cos (\frac{- \sqrt{3^{2} \cdot 5}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1.2.2

Pull terms out from under the radical.

$\cos (\frac{24 v}{7}) \cos (\frac{- 1 \cdot 3 \sqrt{5}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1.2.3

Multiply $- 1$ by $3$ .

$\cos (\frac{24 v}{7}) \cos (\frac{- 3 \sqrt{5}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1.3

Move the negative in front of the fraction.

$\cos (\frac{24 v}{7}) \cos (- \frac{3 \sqrt{5}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1.4

Since $\cos (- \frac{3 \sqrt{5}}{7})$ is an even function, rewrite $\cos (- \frac{3 \sqrt{5}}{7})$ as $\cos (\frac{3 \sqrt{5}}{7})$ .

$\cos (\frac{24 v}{7}) \cos (\frac{3 \sqrt{5}}{7}) + \sin (- \frac{5}{1}) \sin (- \frac{2}{7})$

Step 1.5

Divide $5$ by $1$ .

$\cos (\frac{24 v}{7}) \cos (\frac{3 \sqrt{5}}{7}) + \sin (- 1 \cdot 5) \sin (- \frac{2}{7})$

Step 1.6

Multiply $- 1$ by $5$ .

$\cos (\frac{24 v}{7}) \cos (\frac{3 \sqrt{5}}{7}) + \sin (- 5) \sin (- \frac{2}{7})$

Step 1.7

Since $\sin (- \frac{2}{7})$ is an odd function, rewrite $\sin (- \frac{2}{7})$ as $- \sin (\frac{2}{7})$ .

$\cos (\frac{24 v}{7}) \cos (\frac{3 \sqrt{5}}{7}) + \sin (- 5) (- \sin (\frac{2}{7}))$

Step 2

Reorder factors in $\cos (\frac{24 v}{7}) \cos (\frac{3 \sqrt{5}}{7}) + \sin (- 5) (- \sin (\frac{2}{7}))$ .

$\cos (\frac{24 v}{7}) \cos (\frac{3 \sqrt{5}}{7}) - \sin (- 5) \sin (\frac{2}{7})$