Trigonometry Examples

$2 \cos (210)$

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 third quadrant.

$2 (- \cos (30))$

Step 2

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

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

Step 3

Cancel the common factor of $2$ .

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Step 3.1

Move the leading negative in $- \frac{\sqrt{3}}{2}$ into the numerator.

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

Step 3.2

Cancel the common factor.

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

Step 3.3

Rewrite the expression.

$- \sqrt{3}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$- \sqrt{3}$

Decimal Form:

$- 1.73205080 \dots$