Project point C parallel to AD on line AF. Then this projection H lies on an ellipse, whose center is the middle of AC, points {A,C} being the foci.

- A key feature is the isosceles CHA, which implies the hyperbola property with foci at C, A.

- G is the middle of CE, and I is the middle of CJ.

Additional properties.

- By standard properties of ellipses (see Ellipse.html ) the tangent t

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