-1*1 + 1*1 = 0
gcd(z1,z2) , lcm(z1,z2)
Pl3 = [0 0 0 0 1; 0 0 0 0 0; 0 0 0 0 0; 1 0 0 0 0; 0 1 0 0 0]
Pr3 = [0 0 1 0 0; 0 0 0 0 0; 0 0 0 0 0; 0 1 0 0 0; 0 0 0 0 1]
M= [6 6 4]'
en = [ 0 -0.6 0.8]
T1 = [1 0 -6; 0 1 -4;0 0 1]; T2 = [0 1 0; -1 0 0 ; 0 0 1]; T3 = [1 0 6; 0 1 4;0 0 1]; TT = T3*T2*T1 % =[0 1 2; -1 0 10 ; 0 0 1]; Q = [6 12 12 6 6; -2 -2 4 4 -2; 1 1 1 1 1]; QT = TT*Q; plot(Q(1,:),Q(2,:)); hold on; plot(QT(1,:),QT(2,:),'r'); axis([-15 15 -15 15]); axis square; hold off
w=(0:0.02:5)*2*pi; x= 4*cos(w); z= -4*sin(w); yr= w*0.6/2/pi; yl = -yr; clf; plot3(x,yr,z); hold on; plot3(x,yl,z,'m'); axis equal; hold off