Question 712339
sin(2 theta) +sin( 4 theta) = 0
sin2x +sin4x =0
sin2x+2sin2x+cos2x=0
sin2x(1+cos2x)=0
sin2x=0
2x=0
x=0
or
1+cos2x=0
cos2x=-1
2x=3π/2
x=3π/4