Trigonometry Examples

cos (900)

$\cos (900)$

Step 1

Remove full rotations of

360

$360$ ° until the angle is between

0

$0$ ° and

360

$360$ °.

cos (180)

$\cos (180)$

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 (0)

$- \cos (0)$

Step 3

The exact value of

cos (0)

$\cos (0)$ is

1

$1$ .

- 1 \cdot 1

$- 1 \cdot 1$

Step 4

Multiply

- 1

$- 1$ by

1

$1$ .

- 1

$- 1$