cos²x-sin²x+6sinxcosx-3=0
cos²x-sin²x+6sinxcosx-3[sin²x+cos² ]=0
-2cos²x-4sin²x+6sinxcosx=0↓:[-2cos²x]
2tg²x-3tgx+1=0, tgx=y, tg²x=y²
2y²-3y+1=0, y1=1,y2=0,5
tgx=1, x=π/4+πk
tgx=0,5, x=arctg0,5+πk
