There are different way you could go. One way is to define a time vector
t=0:6;
Define the corner coordinates points.
theta = 0:60:360;
x = cosd(theta);
y = sind(theta);
The initial point appear at the start and at the end. Choose the number of points per side:
M=10;
Create a time vector for interpolating the points:
t1=0:1/M:6;
Interpolate:
x1=interp1(t,x,t1);
y1=interp1(t,y,t1);
Plot x1 versus y1.
plot(x1,y1,'-k.');
axis equal
Done.
