%exm0721_2.m
t=(0:pi/100:pi)';													%<1>
y1=sin(t)*[1,-1];													%<2>
y2=sin(t).*sin(9*t);												%<3>
t3=pi*(0:9)/9;													%<4>
y3=sin(t3).*sin(9*t3);
clf,shg,plot(t,y1,'r:',t,y2,'b',t3,y3,'bo')					%<5>
axis([0,pi,-1,1])													%<6>