Trigonometry Examples

cos (120 °)

$\cos (120 °)$

Step 1

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 (60)

$- \cos (60)$

Step 2

The exact value of

cos (60)

$\cos (60)$ is

\frac{1}{2}

$\frac{1}{2}$ .

- \frac{1}{2}

$- \frac{1}{2}$

Step 3

The result can be shown in multiple forms.

Exact Form:

- \frac{1}{2}

$- \frac{1}{2}$

Decimal Form:

- 0.5

$- 0.5$