koło w kwadracie w kwadracie

% koło w kwadracie w kwadracie
r=2;
x= [-r -r r r -r];
y= [-r r r -r -r];
a = [0 r 0 -r 0];
b = [r 0 -r 0 r];
plot(x,y,'b');
hold on
plot(a,b,'b');
radius=sqrt(r);
th = 0:pi/50:2*pi;
xunit = radius * cos(th);
yunit = radius * sin(th);
h = plot(xunit, yunit,'r');
axis off equal
hold off