solution

>	with(plots): a:=plot([[1,0],[0,1],[-1,0],[0,-1],[1,0]],linestyle=3,color=blue,thickness=1): b:=implicitplot(x^2+y^2=1,x=-1..1, y=-1..1,color=black,thickness=3): c:=plot([[1,1],[-1,1],[-1,-1],[1,-1],[1,1]],linestyle=3,color=blue,thickness=1): display(a,b,c);

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