disp('>> % | ');     % |      disp('>> % |   ROTATION DEFINITION');     % |   ROTATION DEFINITION     disp('>> % |');     % |     x = unit(e1-e2/3); %/     I = e1^e2; %/     angle = pi/6; %/     Rx = gexp(-I*angle)*x; %/     xper = x*I; %/     Iper = I/I3; %/     clf; %/     draw(x,'r'); GAtext(1.1*x+0.1*Iper,'x','r'); %/     draw(I*pi*norm(x)*norm(x),'y'); %/     axis off; %/     disp('>> % | ');     % |      disp('>> % |   A vector x and a plane I containing it');     % |   A vector x and a plane I containing it     disp('>> % |');     % |     GAprompt; %/     %GAview([0 90]); %/     draw(xper,'b'); GAtext(1.1*xper+0.1*Iper,'x_\perp = x {\fontname{times}I}','b'); %/     disp('>> % |');     % |     disp('>> % |   The perpendicular to x in that plane (its dual)');     % |   The perpendicular to x in that plane (its dual)     disp('>> % |');     % |     GAprompt; %/     draw(Rx,'r'); GAtext(1.1*Rx+0.1*Iper,'Rx','r'); %/     DrawPolyline({(Rx^x)/x,Rx,inner(Rx,x)/x},'m'); %/     disp('>> % |');     % |     disp('>> % |   The rotated x can be composed from these, ');     % |   The rotated x can be composed from these,      disp('>> % |   in a coordinate-free manner.');     % |   in a coordinate-free manner.     disp('>> % |');     % |     title('Rx = (cos \phi) x + (sin \phi) (x {\fontname{times}I}) = x (cos \phi + {\fontname{times}I} sin \phi) = x e^{{\fontname{times}I}\phi}'); %/     disp('>> ');