Verified answer

(sin 4x)/(sin 3x * cos x) =1

sin 4x = sin 3x * cos x

sin(3x+x)=sin 3x * cos x

sin 3x * cos x + cos3x*sinx=sin 3x * cos x

cos3x*sinx=0

cos3x=0                                  или                            sin x=0

3x=pi/2 +pi*n, n принадлежит Z                               x=pi*k, k принадлежит Z  

х=pi/6 + pi*n/3,n принадлежит Z