plot( x, -x*a3(1)./a3(2) + b(3)./a3(2),<span class="string">'b-'</span>);
plot( x, -x*a4(1)./a4(2) + b(4)./a4(2),<span class="string">'b-'</span>);
plot( x_c(1) + r*cos(theta), x_c(2) + r*sin(theta), <span class="string">'r'</span>);
plot(x_c(1),x_c(2),<span class="string">'k+'</span>)
xlabel(<span class="string">'x_1'</span>)
ylabel(<span class="string">'x_2'</span>)
title(<span class="string">'Largest Euclidean ball lying in a 2D polyhedron'</span>);
axis([-1 1 -1 1])
axis <span class="string">equal</span