y = sin (n * arcsin x) n > 0
y ' = cos (n*arcsin x) * [ n (1 - x^2)^(-1/2)]
y '' = -sin(n*arcsin x) * [ n (1 - x^2)^(-1/2)]* [ n (1 - x^2)^(-1/2)] + cos(n * arcsinx)* [n * x * (1 - x^2)^(-3/2) ] =
-sin(n*arcsin x)* [n^2 (1- x^2)^-1] + cos (n*arcsinx) * [ nx * (1- x^2)^(-3/2) ] =
[n (1-x)^(-3/2)] * [ xcos(n*arcsinx - nsin(n*arcsinx)(1-x^2)^(1/2) ]
So....
(1 - x^2) y '' - xy ' + n^2y =
(1-x^2) [n (1-x)^(-3/2)] [ xcos(n*arcsinx)- nsin(n*arcsinx)(1-x^2)^(1/2)] -
x [cos (n*arcsin x)] * [ n (1 - x^2)^(-1/2)] + n^2 [sin (n * arcsin x)] =
[ n (1 -x)^(-1/2) ] [ xcos(n*arcsinx) - nsin(n*arcsinx)(1-x^2)^(1/2) ]
- x [cos (n*arcsin x)] * [ n (1 - x^2)^(-1/2)] + n^2 [sin (n * arcsin x)] =
[ xcos(n*arcsinx)] * [ n (1 -x)^(-1/2) ] -
[ n (1 -x)^(-1/2) ] * [ nsin(n*arcsinx)(1-x^2)^(1/2)] -
[x cos (n*arcsin x)] * [ n (1 - x^2)^(-1/2)] + n^2 [sin (n * arcsin x)] =
n^2 [sin (n * arcsin x)] -
n * (1 -x)^(-1/2) * [ nsin(n*arcsinx)] * (1-x^2)^(1/2) =
n^2 [sin (n * arcsin x)] - [ n* n * (1 -x)^(-1/2) * (1 -x)^(1/2) * sin(n*arcsinx) ] =
n^2 [sin (n * arcsin x)] - n^2 [ sin(n * arcsinx)] =
0