Question

Help?!
Sin(x)+Sin(2x)=0

Answer 1

sin(2x) = 2sinxcosx
so sinx + 2sinx cosx = 0
sinx(1 + 2cos x ) = 0
either sinx = 0 or 1 + 2cosx = 0
x = 0 or cos x = -0.5
if you require the solutions in the range 0 to 360 degrees
from sin x = 0:
x = 0, 180 , 360 degrees
from cos x = -0.5
x = 120, 240 degrees