%RHO0 Cauchy integral
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function y=rho0(z)
% For Examples 1 and 2
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%z0=1/sqrt(z-1);
%y=2*z0*atan(z0);
% For Example 3
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%s=symengine;
%y0=vpa(feval(s,'Ei',1,-z));
%y=-exp(-z)*y0;
%For Example 4
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y=vpa(pi)/sqrt(z^2-1);
if subs(z)<0, y=-y; end
