Trigonometry Examples

$\sin (- x) \cos (3 x) - \cos (- x) \sin (3 x)$

Step 1

Since $\sin (- x)$ is an odd function, rewrite $\sin (- x)$ as $- \sin (x)$ .

$- \sin (x) \cos (3 x) - \cos (- x) \sin (3 x)$

Step 2

Since $\cos (- x)$ is an even function, rewrite $\cos (- x)$ as $\cos (x)$ .

$- \sin (x) \cos (3 x) - \cos (x) \sin (3 x)$