Trigonometry Examples

$\cos (2 \cdot (- \frac{4}{5}))$

Step 1

Multiply $2 (- \frac{4}{5})$ .

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Step 1.1

Multiply $- 1$ by $2$ .

$\cos (- 2 (\frac{4}{5}))$

Step 1.2

Combine $- 2$ and $\frac{4}{5}$ .

$\cos (\frac{- 2 \cdot 4}{5})$

Step 1.3

Multiply $- 2$ by $4$ .

$\cos (\frac{- 8}{5})$

Step 2

Move the negative in front of the fraction.

$\cos (- \frac{8}{5})$

Step 3

Since $\cos (- \frac{8}{5})$ is an even function, rewrite $\cos (- \frac{8}{5})$ as $\cos (\frac{8}{5})$ .

$\cos (\frac{8}{5})$

Step 4

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{8}{5})$

Decimal Form:

$- 0.02919952 \dots$