Find the Exact Value cos(660 degrees )

$\cos (660 °)$

Remove full rotations of $360$ ° until the angle is between $0$ ° and $360$ °.

$\cos (300)$

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.

$\cos (60)$

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

$\frac{1}{2}$

The result can be shown in multiple forms.

Exact Form:

$\frac{1}{2}$

Decimal Form:

$0.5$