Егэ ! ! много ! 2sin^4(2x)+cos(4x)-1=0 б) [2п; 3п]

2sin^42x+1-2sin²2x-1=0
2sin^42x-2sin²2x=0
2sin²2x(sin²2x-1)=0
sin2x=0⇒2x=πn,n∈z⇒x=πn/2,n∈z
2π≤πn/2≤3π
4≤n≤6
n=4⇒x=2π
n=5⇒x=5π/2
x=6⇒x=3π
sin²2x=1
sin2x=-1⇒2x=-π/2+2πk,k∈z⇒x=-π/4+πk,k∈z
2π≤-π/4+πk≤3π
8≤-1+4k≤12
9≤4k≤13
9/4≤k≤13/4
k=3⇒x=-π/4+3π⇒x=11π/4
sin2x=1⇒2x=π/2+2πm,m∈z⇒x=π/4+πm,m∈z
2π≤π/4+πm≤3π
8≤1+4m≤12
7≤4m≤11
7/4≤m≤11/4
m=2⇒x=π/4+2π=9π/4