solve the eqns for 0<=x<=180
1. sin3x+sinx=0
(i don't get my friend's working):
2 sin2xcosx=0
2(2sinxcosx)(cosx)=0
(4sinxcosx)(cosx)=0
4 sinx=0
sinx=0
x= 0, 180
what I don't get is how the (4 sin x cos x) (cos x) = 0 became just 4 sin x = 0.
she said she canceled it and gave no further explanation. i don't get it, because it's multiply, how could she have canceled the cos x-es out.
2. sin5x-sinx=0
i got up until:
2 cos 3x sin 2x = 0
2 (4cos*3x-3cosx) (2 sinx cosx) = 0