perp

p1 = [5 2];

p2 = [2 4];

k1 = [0.4 0.8];

k2 = [0.9 0.1];

p= [p1; p1+10*k1];

plot(p(:,1),p(:,2),'k','LineWidth',2);

hold on

plot(p1(1),p1(2),'ko','MarkerSize',7);

p= [p2; p2+10*k2];

plot(p(:,1),p(:,2),'b','LineWidth',2);

plot(p2(1),p2(2),'bo','MarkerSize',7);

hold off

grid

A = [k1' -k2'];

b = [p2-p1]';

q = A\b;

pi = p1+q(1)*k1;

hold on

plot(pi(1),pi(2),'rs','MarkerSize',11);

D =det(A);

Ai = [A(2,2) -A(1,2); -A(2,1) A(1,1)];

qt = Ai/D*b;