You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rot3.m
    path of file: ./repos/Orbital_Mechanics
    
    the code of the file until where you have to start completion: function rot3 = rot3(th)
    %% Create the rotation matrix about the y-axis
    %
    % Jeremy Penn
    % 18 October 2017
    %
    % Revision  22/09/17
    %           
    % function rot3 = rot3(th)

    
function rot3 = rot3(th)
    %% Create the rotation matrix about the y-axis
    %
    % Jeremy Penn
    % 18 October 2017
    %
    % Revision  22/09/17
    %           
    % function rot3 = rot3(th)
    %
    % Purpose:  This function calculates the rotation matrix about the
    %           z-axis
    % 
    % Inputs:   o th - The rotation angle.
    % 
    % Output:   o rot3 - Rotation matrix about the x-axis.
    %
    
    %% Create the matrix
    
    rot3 = [cos(th),sin(th),0;-sin(th),cos(th),0;0,0,1];
end