1) cos x/8 = (-√2)/2 ;
x/8 = ±(π -π/4) +2π*k , k∈Z.
x =± 6π +16π*k , k∈Z.
2) sin(3x/5 +π/3) =√3/2 * * * 3x/5 +π/3 =(-1)^k +π*k * * *
a) 3x/5 +π/3 =π/3 + 2π*k , k∈Z ⇒ x = 10π/3*k , k∈Z.
b) 3x/5 +π/3 = (π -π/3) +2π*k , k∈Z⇒x = 5π/9 + 10π/3*k , k∈Z
3) -tq(2x -π/6) = 1 ;
tq(2x -π/6) = -1 ;
2x -π/6 = -π/4 +π*k , k∈Z.
x = -π/24 + π/2*k ,k∈Z.