I was wondering why I was having difficulty plotting
`PartialD[LegendreP[l, m, Cos[x]], x]`, where $l\in\mathbb{N}$ and $m\in\{-l,~-l+1,\cdots,l-1,~l\}$ as per usual for this function. I even tried the equivalent `Subscript[\[PartialD], x]LegendreP[l, m, Cos[x]]` (I am aware that doesn't come out neatly on this page, but that's what copying the code gives after pasting it). Is it a variable type issue and if so, how can I get around this?