[tex]\displaystyle\\
\sin (a) = \frac{1}{5}\\\\
a)~~ \sin (-a) = -\sin a = -\frac{1}{5}\\\\
b)~~ \sin (a+60\pi) = \sin (a+30\cdot2\pi)=\sin (a) = \frac{1}{5}\\\\
c)~~ \sin (a-20\pi) = \sin (a-10\cdot2\pi)=\sin (a) = \frac{1}{5}\\\\
d)~~ \sin (2\pi-a) =\sin (-a) = -\sin a = -\frac{1}{5}\\\\
e)~~ \sin (16\pi-a) = \sin (8\cdot 2\pi-a) = \sin (-a) = -\sin a = -\frac{1}{5}[/tex]
