(i) Let X be a curve, and p∈X be a smooth point on X. Define what a local parameter at p is.
Now let f:X→Y be a rational map to a quasi-projective variety Y. Show that if Y is projective, f extends to a morphism defined at p.
Give an example where this fails if Y is not projective, and an example of a morphism f:C2\{0}→P1 which does not extend to 0.
(ii) Let V=Z(X08+X18+X28) and W=Z(X04+X14+X24) be curves in P2 over a field of characteristic not equal to 2 . Let ϕ:V→W be the map [X0:X1:X2]↦[X02:X12:X22]. Determine the degree of ϕ, and the ramification ep for all p∈V.