How to call Method(Function) from one webpage to another webpage using Master page in ASP.NET C#

Question

I have created a master page Login_Nav and created two pages AuthenticationMethods.aspx and password.aspx with masterpage Login_Nav.master.

I have also created a method CheckAuth() in AuthenticationMethods.aspx page and I want to call that method into password.aspx page for that I have created the instance

Model_AuthenticationMethods authenticationMethods = new Model_AuthenticationMethods();

and it is throwing an error

Are you missing a using directive or an assembly reference

I'm not sure how to call that method CheckAuth() where I want, below is my code

Login_Nav master page:

<%@ Master Language="C#" AutoEventWireup="true" CodeFile="Login_Nav.master.cs" Inherits="Login_Nav" %>
public partial class Login_Nav : System.Web.UI.MasterPage
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
}

AuthenticationMethods aspx page with master page:

<%@ Page Title="" Language="C#" MasterPageFile="~/Login_Nav.master" AutoEventWireup="true" CodeFile="AuthenticationMethods.aspx.cs" Inherits="Model_AuthenticationMethods" %>
public partial class Model_AuthenticationMethods : System.Web.UI.Page
{
    public void CheckAuth()
    {
        // my logic will go here
    }
}

password.aspx page with master page - I want to call the CheckAuth(); method in password.aspx page:

<%@ Page Title="" Language="C#" MasterPageFile="~/Login_Nav.master" AutoEventWireup="true" CodeFile="password.aspx.cs" Inherits="password" %>
public partial class Model_Data : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // Creating an instance of Model_AuthenticationMethods
        Model_AuthenticationMethods authenticationMethods = new Model_AuthenticationMethods(); //getting error "are you missing a using directive or an assembly reference"

        authenticationMethods.CheckAuth()

        // CheckAuth();
    }
}

Please suggest how to call that method {creating an instance or using inheritance concept}

I don't have a good knowledge to achieve this concept