Trigonometry Examples

$4 \cos (\frac{2 π}{3})$

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.

$4 (- \cos (\frac{π}{3}))$

Step 2

The exact value of $\cos (\frac{π}{3})$ is $\frac{1}{2}$ .

$4 (- \frac{1}{2})$

Step 3

Cancel the common factor of $2$ .

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Step 3.1

Move the leading negative in $- \frac{1}{2}$ into the numerator.

$4 (\frac{- 1}{2})$

Step 3.2

Factor $2$ out of $4$ .

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

Step 3.3

Cancel the common factor.

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

Step 3.4

Rewrite the expression.

$2 \cdot - 1$

Step 4

Multiply $2$ by $- 1$ .

$- 2$