## Algebra 2 (1st Edition)

$\tan(x)=\frac{\sin(x)}{\cos(x)},\cos(-3x)=\cos(3x),\sin(-x)=-\sin(x),\cos(x-\pi/2)=\sin(x)$.
Using the definition of a trigonometric identity, the following are identities among the studied equations: $\tan(x)=\frac{\sin(x)}{\cos(x)},\cos(-3x)=\cos(3x),\sin(-x)=-\sin(x),\cos(x-\pi/2)=\sin(x)$.