Can someone help me out with what I believe who.d be a straight chain rule application?
D/dx (dy/dx)^2
I would think, applying the chain rule, you get
2 (dy/dx) d/dx (dy/dx) = 2 (dy/dx) (d2y/dx2)
But, from the papers I checked, the (dy/dx) in the answer goes away, leaving just
2...