How to plot trapezoids under a curve?

please do not use any symbolic math toolbox since I will do this in an executable later

[Erwin Avendaño]

   a=str2double(get(handles.edit7,'string'));
b=str2double(get(handles.edit6,'string'));
xx=a:0.01:b;
f=inline(get(handles.edit1,'string'));
y1=f(xx);
axes(handles.axes3);
plot(xx,y1,'r*','LineWidth',3)