My "geometry English" is not good so I hope you can understand from picture.

I need to prove that EFGH is tangential. Angles DHS,DGS,CFS,AES are right angles. Thanks.

Originally Posted by kicma
My "geometry English" is not good so I hope you can understand from picture.

I need to prove that EFGH is tangential. Angles DHS,DGS,CFS,AES are right angles. Thanks.
Hello,

I don't understand what is meant by your drawing. I've attached a sekant-tangent-quadrilateral:

Please tell us which point is your point S: The crosspoint of the red sekants or the midpoint of the inner circle $k_i$?