Explain why the pair of functions $y_1(x) = x$ and $y_2(x) = \sin(x)$ cannot form a set of fundamental solutions to a second order homogeneous differential equiationon the interval $(-1,1)$.
$W = x\cos(x) - \sin(x)$
If $x = 0$ then:
$W = 0\cos(0) - \sin(0)$
$W = 0$
I'm not sure if this was what i\I was supposed to do. Any help will be appreciated.