sin2x+2cos^2X=0

sin2x+1=0

sin4x-sin7x=0

sin2x+2cos^2X=0

2sinxcosx+2cos^2x=0

2cosx (sinx+cosx) = 0

x=П/2 (2k+1)

sinx+cosx=0

tgx=-1

x=-П/4+Пk

sin2x+1=0 sin2x=-1 2x=-П/2+2 Пk x=-П/4+Пk

sin4x-sin7x=0 - 2sin3x/2cos11x/2=0

sin3x/2=0 3x/2=Пk x=2 Пk/3

cos11x/2=0

11x/2=П/2 (2k+1)

x=П/11 (2k+1)