#### Answer

(a) $\sin{3\pi}=0$
(b) $\cos{3\pi}=-1$
(c) $\tan{3\pi}=\dfrac{0}{-1}=0$

#### Work Step by Step

Using Figure 13 on page 579 of this book, the angle $3\pi$ intersects the unit circle at the point $(-1, 0)$.
RECALL:
In a unit circle,
(1) $\cos{s} = x$
(2) $\sin{s} = y$
(3) $\tan{s} = \dfrac{y}{x}$
Thus, use the definitions above to obtain:
(a) $\sin{3\pi}=0$
(b) $\cos{3\pi}=-1$
(c) $\tan{3\pi}=\dfrac{0}{-1}=0$