MATLAB GUIのスライダーを使って楕円を作りたい

MATLAB GUIのスライダーを使って楕円を作りたい
ここに実現したいことを箇条書きで書いてください。

前提

ここに質問の内容を詳しく書いてください。
なぜaが認識されず、エラーが起きているのか教えてくれませんか。
どうすれば楕円が書けるでしょうか。

発生している問題・エラーメッセージ

エラーメッセージ

関数または変数 'a' が認識されません。

エラー: exercise14_2>slider1_CreateFcn (行 123)
x = a*cosd(t);

エラー: gui_mainfcn (行 95)
feval(varargin{:});

エラー: exercise14_2 (行 42)
gui_mainfcn(gui_State, varargin{:});

エラー: matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)exercise14_2('slider1_CreateFcn',hObject,eventdata,guidata(hObject))

該当のソースコード

MATLAB

ソースコード

function varargout = exercise14_2(varargin)
% EXERCISE14_2 MATLAB code for exercise14_2.fig
% EXERCISE14_2, by itself, creates a new EXERCISE14_2 or raises the existing
% singleton*.
%
% H = EXERCISE14_2 returns the handle to a new EXERCISE14_2 or the handle to
% the existing singleton*.
%
% EXERCISE14_2('CALLBACK',hObject,eventData,handles,...) calls the local
% function named CALLBACK in EXERCISE14_2.M with the given input arguments.
%
% EXERCISE14_2('Property','Value',...) creates a new EXERCISE14_2 or raises the
% existing singleton*. Starting from the left, property value pairs are
% applied to the GUI before exercise14_2_OpeningFcn gets called. An
% unrecognized property name or invalid value makes property application
% stop. All inputs are passed to exercise14_2_OpeningFcn via varargin.
%
% *See GUI Options on GUIDE's Tools menu. Choose "GUI allows only one
% instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help exercise14_2

% Last Modified by GUIDE v2.5 09-Feb-2023 14:37:50

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @exercise14_2_OpeningFcn, ...
'gui_OutputFcn', @exercise14_2_OutputFcn, ...
'gui_LayoutFcn', [] , ...
'gui_Callback', []);
if nargin && ischar(varargin{1})
gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT

% --- Executes just before exercise14_2 is made visible.
function exercise14_2_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% varargin command line arguments to exercise14_2 (see VARARGIN)

% Choose default command line output for exercise14_2
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

% UIWAIT makes exercise14_2 wait for user response (see UIRESUME)
% uiwait(handles.figure1);

% --- Outputs from this function are returned to the command line.
function varargout = exercise14_2_OutputFcn(hObject, eventdata, handles)
% varargout cell array for returning output args (see VARARGOUT);
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;

% --- Executes on slider movement.
function slider2_Callback(hObject, eventdata, handles)
% hObject handle to slider2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
b = get(hObject,'Value');
% Hints: get(hObject,'Value') returns position of slider
% get(hObject,'Min') and get(hObject,'Max') to determine range of slider

% --- Executes during object creation, after setting all properties.
function slider2_CreateFcn(hObject, eventdata, handles)
% hObject handle to slider2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called

% Hint: slider controls usually have a light gray background.
if isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor',[.9 .9 .9]);
end

% --- Executes on slider movement.
function slider1_Callback(hObject, eventdata, handles)
% hObject handle to slider1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
a = get(hObject,'Value');
% Hints: get(hObject,'Value') returns position of slider
% get(hObject,'Min') and get(hObject,'Max') to determine range of slider

% --- Executes during object creation, after setting all properties.
function slider1_CreateFcn(hObject, eventdata, handles)
% hObject handle to slider1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called

% Hint: slider controls usually have a light gray background.
if isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor',[.9 .9 .9]);
end

axis([-100 100 -100 100]);
t = 0:360;
x = acosd(t);
y = bsind(t);
plot(x,y);
drawnow;

試したこと

ここに問題に対して試したことを記載してください。

補足情報（FW/ツールのバージョンなど）

ここにより詳細な情報を記載してください。