Trigonometry Examples

$\cos (\frac{- 20 π}{5})$

Step 1

Cancel the common factor of $- 20$ and $5$ .

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Step 1.1

Factor $5$ out of $- 20 π$ .

$\cos (\frac{5 (- 4 π)}{5})$

Step 1.2

Cancel the common factors.

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Step 1.2.1

Factor $5$ out of $5$ .

$\cos (\frac{5 (- 4 π)}{5 (1)})$

Step 1.2.2

Cancel the common factor.

$\cos (\frac{5 (- 4 π)}{5 \cdot 1})$

Step 1.2.3

Rewrite the expression.

$\cos (\frac{- 4 π}{1})$

Step 1.2.4

Divide $- 4 π$ by $1$ .

$\cos (- 4 π)$

Step 2

Add full rotations of $2 π$ until the angle is greater than or equal to $0$ and less than $2 π$ .

$\cos (0)$

Step 3

The exact value of $\cos (0)$ is $1$ .

$1$