Calc

I'm feeling retarded and need halp:
lim x->0 sin4x/sin6x=?
also
Given y=sin2x-2sinx, find dy/dx=0
also
Given f(x)=xg(x^2), find f'' in terms of g,g',g''
Any help would be much appreciated!

2/3

sin(x) approaches x as approaches 0
therefore you can say:
lim(x->0) sin(4x)/sin(6x) =>
lim(x->0) 4x/6x =>
2/3