if ~exist('x'), x = '[-2*pi, 2*pi]'; end

f1 = '1/(5+4*cos(x))' 
f2 = '(exp(x/pi)*4*cos(x))' 
f3 = '(exp(-x/pi)*4*sin(x))' 

figure(1)
T1 = uicontrol('pos',[.03 .03 .07 .07],'string','f1','Callback',...
     'ff1');
figure(2)
T1 = uicontrol('pos',[.03 .03 .07 .07],'string','f2','Callback',...
     'ff2');
figure(3)
T3 = uicontrol('pos',[.03 .03 .07 .07],'string','f3','Callback','ff3');