sinx+sin6x+sin2x+sin5x+sin3x+sin4x=0
\Leftrightarrow2sin7/2xcos5/2x+2sin7/2xcos3/2x+2sin7/2xcosx/2=0
\Leftrightarrowsin7/2x=o
hoac cos5x/2+cos3x/2+cosx/2=0
\Leftrightarrow2cos2xcosx/2+cosx/2=0
\Leftrightarrowcosx/2=0
hoac 2cos2x=-1
den day ban lam not nhe!