## Functions Modeling Change: A Preparation for Calculus, 5th Edition

$\sin 0^\circ=0$ $\cos 0^\circ=1$ $\tan 0^\circ = 0$
Sin and cos values should be simpler to calculate using the unit circle. An angle of $0^\circ$ from the horizontal should give an $x$ value or cosine value of $\cos 0^\circ=1$ and a $y$ value or sine value of $\sin 0^\circ=0$. Since $\tan 0^\circ = \frac{\sin 0^\circ}{\cos 0^\circ}$, the expression becomes $$\tan 0^\circ = \frac{0}{1}=0$$