Precalculus Examples

$\cos (- 210)$

Step 1

Find the value using the definition of cosine.

$\cos (- 210) = \frac{adjacent}{hypotenuse}$

Step 2

Substitute the values into the definition.

$\cos (- 210) = \frac{- \frac{\sqrt{3}}{2}}{1}$

Step 3

Divide $- \frac{\sqrt{3}}{2}$ by $1$ .

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

Step 4

The result can be shown in multiple forms.

Exact Form:

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

Decimal Form:

$- 0.86602540 \dots$

Step 5

$[\begin{array}{c} x^{2} & \frac{1}{2} \\ \sqrt{π} & \int x d x \end{array}]$