Linear Algebra - Rotate A Triangle

So this is the code provided by our lecturer.

figure(1), clf
fill(X,Y,’g’,’edgecolor’,’k’,’linewidth’,1), hold on
axis equal, axis([-1.5 2 -0.1 2]), axis manual; 
pause(1);
v=pi/6; A=[cos(v) -sin(v); sin(v) cos(v)];
P=[X;Y];  
for i=1:3
     P=A*P;
     fill(P(1,:),P(2,:),’g’,’edgecolor’,’r’,’linewidth’,1), pause(1) 
end
plot(0,0,’ko’,’linewidth’,2,’markersize’,2)  %origo

And the assignment is to rotate a triangle which is created by defining the row matrices X and Y and I don't know how to create a triangle.