I'm using the word "cusp" informally here, I apologize if there is a formal definition for it. What I'm looking for is a point where the derivative is non-continuous, I think.
I have a a sequence of two-dimensional points on a parametric curve (equations for the curve itself are unknown) and I want to find "sharp" points on the curve. I'm sorry for not being more clear, I don't have the background to use all the correct terminology.