1. 3x=π/2+πn, n∈Z
x=π/6+πn/3, n∈Z
2. x/2=-π/4+πn, n∈Z
x=-π/2+2πn, n∈Z
3. -4x=π/4+πn, n∈Z
x=-π/16+πn/4, n∈Z
4. 3x-π/6=π/6+πn, n∈Z
3x=π/3+πn, n∈Z
x=π/9+πn/3, n∈Z
5. π/6-2x=π-π/6+πn
-2x=2π/3+πn
x=-π/3+πn/2, n∈Z
4sin3x+cos²3x=0
4sin3x+1-sin²3x=0
sin²3x-4sin3x-1=0
Пусть sin3x=m, тогда
m²-4m-1=0
D=4²-4*(-1)=20
√D=2√5
m1=2+√5-пост. корень
m2=2-√5
sin3x=2-√5
3x=(-1)ⁿ*arcsin(2-√5)+Пn
x=(-1)ⁿ*arcsin(2-√5)/3+Пn/3
№80.
1) 3х = -6
х = (-6):3
х = -2
2) х+3 = 6
х = 6-3
х = 3
3) 4х-4 = х+5
4х-х = 5+4
3х = 9
х = 9:3
х = 3
4) 5х-8 = 2х+4
5х-2х = 4+8
3х = 12
х = 12:3
х = 4
№81.
1) х+5 = -6
х = - 6-5
х = -11
2) 4-х = -1
-х = -1-4
-х = -5
х = 5
3) 2х - 1 = 0
2х = 0+1
2х = 1
х = 1:2
х = 0.5
4) 3х+2 = 0
3х = 0-2
3х = -2
х = (-2):3
х = -2/3