4cos(x)*cos(2x)*cos(4x)=sin(8x)
sin2(A)=2sin(A) cos(A) (Identity)
sin(8x)=sin(2xx4x) (4x=A)
sin(2xx4x)=2cos(4x)sin(4x)
4cos(x)*cos(2x)*cos(4x)=2cos(4x)*sin(4x)
Divide by cos(4x) both sides
4cos(x)*cos(2x)=2sin(4x)
Again
sin(4x)=sin(2xx2x) (2x=A)
sin(2xx2x)=2cos(2x)sin(2x)
4cos(x)*cos(2x)=4cos(2x)*sin(2x)
Divide by cos(2x) both sides
4cos(x)=4sin(2x) and divide by 4
cos(x)=sin(2x)
sin(2x)=sin(2xxx) (x=A)
sin(2xxx)=2cos(x)*sin(x)
cos(x)=2cos(x)*sin(x)
So, sin(x)=1/2
x=30