Precalculus Examples

\cos (\frac{10 π}{3})

$\cos (\frac{10 π}{3})$

Step 1

Subtract full rotations of

2 π

$2 π$ until the angle is greater than or equal to

0

$0$ and less than

2 π

$2 π$ .

\cos (\frac{4 π}{3})

$\cos (\frac{4 π}{3})$

Step 2

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the third quadrant.

- \cos (\frac{π}{3})

$- \cos (\frac{π}{3})$

Step 3

The exact value of

\cos (\frac{π}{3})

$\cos (\frac{π}{3})$ is

\frac{1}{2}

$\frac{1}{2}$ .

- \frac{1}{2}

$- \frac{1}{2}$

Step 4

The result can be shown in multiple forms.

Exact Form:

- \frac{1}{2}

$- \frac{1}{2}$

Decimal Form:

- 0.5

$- 0.5$

\cos (\frac{10 π}{3})

$\cos (\frac{10 π}{3})$

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