With this second one, I understand why sine x cannot equal 0 but I do not understand/have no idea what kpi is
Hello juliakOK. I now know what kpi is: . But I still don't see where is relevant in your original post.
However, what you have written here is easy to understand. If , then cannot be a multiple of . (Since the sine of all multiples of is zero.) In other words:Have we cleared all this up now?
, where is an integer
Grandad