[tex]sinx=- \frac{1}{2} =>sinx=-sin \frac{\pi}{6}=>sinx+sin \frac{\pi}{6}=0=>
2sin \frac{x+ \frac{\pi}{6} }{2} \cdot cos \frac{x-\frac{\pi}{6}}{2}=0[/tex]
[tex] sin \frac{x+ \frac{\pi}{6} }{2}=0=>\frac{x+ \frac{\pi}{6} }{2}=0 sau \pi=>x=2\pi-\frac{\pi}{6}= \frac{11\pi}{6} \\ [/tex]
[tex]cos \frac{x-\frac{\pi}{6}}{2}=0=>\frac{x-\frac{\pi}{6}}{2}= \frac{\pi}{2} sau \frac{3\pi}{2} =>x=\pi+ \frac{\pi}{6} = \frac{7\pi}{6} [/tex]
