#### Answer

(a) $\sin{\frac{\pi}{2}}=1$
(b) $\cos{\frac{\pi}{2}}=0$
(c) $\tan{\frac{\pi}{2}}=\dfrac{1}{0}, \text{ undefined}$

#### Work Step by Step

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