source 2008 Bernstein--Lange--Rezaeian Farashahi compute X3 = 1 + (d1 + d2(X1^2+Y1^2) + Y1^2+Y1^4)/(d1 + X1^2 + Y1^2 + (d2/d1)(X1^4+Y1^4)) compute Y3 = 1 + (d1 + d2(X1^2+Y1^2) + X1^2+X1^4)/(d1 + X1^2 + Y1^2 + (d2/d1)(X1^4+Y1^4))