Chapter 6 - The Circular Functions and Their Graphs - 6.2 The Unit Circle and Circular Functions - 6.2 Exercises - Page 588: 15

(a) $\sin{2\pi}=0$ (b) $\cos{2\pi}=1$ (c) $\tan{2\pi}=0$

Using Figure 13 on page 579 of this book, the angle $\pi$ 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) $\sin{2\pi}=0$ (b) $\cos{2\pi}=1$ (c) $\tan{2\pi}=\dfrac{0}{1}=0$