Решите уравнение, заранее sin3x+sin5x+sin8x=0

(sin5x+sin3x) +sin2*4x =0 ;
2sin(5x+3x)/2*cos(5x-3x)/2 +2sin4x*cos4x=0 ;
2sin4x(cosx +cos4x) =0 ; 
a) sin4x =0 ;
4x =π*k , k∈Z;
x = π/4   ,k∈Z .
b) cos4x +cosx =0 ;
2cos5x/2*cos3x/2 = 0;
[cos5x/2 =0 ;cos3x/2 =0.
[5x/2 =π/2 +π*k ; 3x/2 =π/2 +π*k .
[x =  π/5 + 2π/5*k  ; x =  π/3 + 2π/3*k  ; k∈Z .
ответ:  π*k  ;  π/3 + 2π/3*k  ; π/5 + 2π/5*k ; k∈Z .