Trigonometry Examples

$3 \cos (120)$

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.

$3 (- \cos (60))$

Step 2

The exact value of $\cos (60)$ is $\frac{1}{2}$ .

$3 (- \frac{1}{2})$

Step 3

Multiply $3 (- \frac{1}{2})$ .

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Step 3.1

Multiply $- 1$ by $3$ .

$- 3 (\frac{1}{2})$

Step 3.2

Combine $- 3$ and $\frac{1}{2}$ .

$\frac{- 3}{2}$

Step 4

Move the negative in front of the fraction.

$- \frac{3}{2}$

Step 5

The result can be shown in multiple forms.

Exact Form:

$- \frac{3}{2}$

Decimal Form:

$- 1.5$

Mixed Number Form:

$- 1 \frac{1}{2}$