Question 935775
use angle subtraction identity to get 

{{{sin(3x-6x)=-0.9}}}

then since sine is an odd function


{{{-sin(3x)=-0.9}}}


which leads to


{{{sin(3x)=0.9}}}


{{{arscin(sin(3x))=arcsin(0.9)}}}

{{{3x=arcsin(0.9)+2*pi*n}}}


{{{x=(2*pi*n+arcsin(0.9))/3}}}