two basic Forms authentication issue in ASP.Net

I am developing on Windows Server 2008 with VSTS 2008 + C# + .Net 3.5 to develop an ASP.Net application using Forms authentication. I am learning Forms authentication from http://msdn.microsoft.com/en-us/library/aa480476.aspx

I have two basic questions,

1. I think after call method "FormsAuthentication.SetAuthCookie", the user should be authenticated, why in step 9, it is said "9.The FormsAuthenticationModule class detects the forms authent开发者_开发问答ication cookie and authenticates the user"? Seems we need authenticate user twice, both in step 6 (when we call FormsAuthentication.SetAuthCookie) and in step 9? If yes, why we need to authenticate user twice?

2. In order to implement a custom Forms authentication (I have a custom user credential database which is used for Forms authentication), do I need to call 4 methods -- "new FormsAuthenticationTicket", "FormsAuthentication.Encrypt", new HttpCookie and Response.Cookies.Add(authCookie)? Or just need to call "FormsAuthentication.SetAuthCookie"?

1. You perform step 6, the Forms Library module performs step 9.
2. No, just call SetAuthCookie / RedirecterFormLogin.