Precalculus Examples

$\cos (- 150)$

Step 1

The complement of $\cos (- 150)$ is the angle that when added to $\cos (- 150)$ forms a right angle ( $90 °$ ).

$90 ° - \cos (- 150)$

Step 2

Simplify each term.

Tap for more steps...

Step 2.1

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 third quadrant.

Step 2.2

The exact value of $\cos (30)$ is $\frac{\sqrt{3}}{2}$ .

$90 + \frac{\sqrt{3}}{2 °}$

Step 2.3

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

Tap for more steps...

Step 2.3.1

Multiply $- 1$ by $- 1$ .

Step 2.3.2

Multiply $\frac{\sqrt{3}}{2}$ by $1$ .

$90 + \frac{\sqrt{3}}{2 °}$

Step 3

The result can be shown in multiple forms.

Exact Form:

$90 + \frac{\sqrt{3}}{2 °}$

Decimal Form:

$90.86602540 \dots$