Let G:E -> E' and H: E->E' be isogenies between elliptic curves. Then (G+H)^=G^+H^ (G^ means dual isogeny od G).
I'm reading "The Arithmetic of Elliptic Curves[Silverman]" Actually it's a part of Theorem in Chap3.6. I can't understand its proof. In particular, "ord_{P_1}(f)=e_{G}(p_1)" this equality. (Sorry,I can't whole content of proof.) Somebody, help me!
