Algebra Examples

cos (150 °)

$\cos (150 °)$

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 (30)

$- \cos (30)$

Step 2

The exact value of

cos (30)

$\cos (30)$ is

\frac{\sqrt{3}}{2}

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

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

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

Step 3

The result can be shown in multiple forms.

Exact Form:

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

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

Decimal Form:

- 0.86602540 \dots

$- 0.86602540 \dots$