Precalculus Examples

$\sin (- 1530)$

Step 1

Add full rotations of $360$ ° until the angle is between $0$ ° and $360$ °.

$\sin (270)$

Step 2

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because sine is negative in the third quadrant.

$- \sin (90)$

Step 3

The exact value of $\sin (90)$ is $1$ .

$- 1 \cdot 1$

Step 4

Multiply $- 1$ by $1$ .

$- 1$