You wrote the sin. cos and tan funcitons beggining with with capital letters:
Sin, Cos and Tan in your code.
Write the functions like this:
% --- Executes on button press in Tan.
function Tan_Callback(hObject, eventdata, handles)
% hObject handle to Tan (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
textstring = get(handles.text1,'string');
textstring = strcat(textstring,'tan')
set(handles.text1,'string',textstring);
% --- Executes on button press in Sin.
function Sin_Callback(hObject, eventdata, handles)
% hObject handle to Sin (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
textstring = get(handles.text1,'string');
textstring = strcat(textstring,'sin')
set(handles.text1,'string',textstring);
% --- Executes on button press in Cos.
function Cos_Callback(hObject, eventdata, handles)
% hObject handle to Cos (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
textstring = get(handles.text1,'string');
textstring = strcat(textstring,'cos')
set(handles.text1,'string',textstring);
