cosx, sinx, ex, and e-x are LI or LD ( 0 =or< x =or< 1)
I can see without calculation that it is LI but I do not know how to prove it.
I tried to use Wronskian Determinant but it gets really messy
cosx sinx ex e-x
-sinx cosx ex -ex
-cosx -sinx ex e-x
sinx -cosx ex e-x
Someone please suggest a better and quicker way...