[tex]1)2sin^2-cosx-1=0[/tex]
[tex]2)tgx-2ctgx+1=0[/tex]
[tex]3)3cos^26x+8sin3xcos3x-4=0[/tex]

1) 2-2cos^2x-cosx-1=01-2cos^2x-cosx=02cos^2x+cosx-1=0  cosx=t   2t^2+t-1=0t1=-1  t2=1/2x1=П+2Пkx2=+-П/3+2Пk2)tgx=t t-2/t+1=0   t^2+t-2=0t1=1     x=П/4+Пkt2=-2   x=-arctg2+пk3) 3-3sin^2(6x)-4+4sin6x=0sin6x=t4t-3t^2-1=03t^2-4t+1=0t1=1 sin6x=1   6x=П/2+2Пk    x=п/12+Пk/3t2=1/3  sin6x=1/3 6x=(-1)^karcsin(1/3)+Пk                               x=1/6*(-1)^k*arcsin(1/3)+Пk/6