I don't know Haskell at all, the ~"all functions only have one argument" concept interests me.

>"had an easy time explaining how (2 * 3) really is two functions, each with one argument and one result, and he drew it out on paper nicely" //

So, like you pass the multiply function an argument which is a list (2, 3). Or is it more like you pass the multiply function the first operand (2 in this case) and it returns a function multiply-by-2 which you pass the second operand? The latter seems like it would get sub-optimal pretty quickly. Mind you surely here the compiler produces the same sort of assembly [repeated addition here] making it just a way to abstract around an alternate mental model.

I've just looked at https://wiki.haskell.org/Currying, could someone walk through how something like arcsin(0) works - that's probably a bad example - something that takes a single variable input but has multiple solutions (returns n.π in this case, but say sqrt or an anagram function or ...)?

I'm sure you can tell I'm not a computer scientist, not even a programmer ...