4sin^6x=1-sin^2x
4sin^6x+sin^2x-1=0
4t^3+t-1=0
t=1/2
(t-1/2)(4t^2+2t+2)=0
sin^2x=1/2
sinx=+-sqrt(2)/2
x1=(-1)^k*П/4+Пk
x2=(-1)^(k+1)*П/4+Пk