Trigonometry Examples

cos (870)

$\cos (870)$

Step 1

Remove full rotations of

360

$360$ ° until the angle is between

$0$ ° and

$360$ °.

$\cos (150)$

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 second quadrant.

$- \cos (30)$

Step 3

The exact value of

$\cos (30)$ is

$\frac{\sqrt{3}}{2}$ .

$- \frac{\sqrt{3}}{2}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$- \frac{\sqrt{3}}{2}$

Decimal Form:

$- 0.86602540 \dots$

$\cos (870)$

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