The inverse surfaces of tangent developables with respect to s_{c}(r)
  In this paper, we define the inverse surface of a tangent developable surface with respect to the sphere S_{c}(r) with the center $c\in \mathbb{E}^{3}$ and the radius r in 3-dimensional Euclidean space $\mathbb{E}^{3}$. We obtain the curvatures, the Christoffel symbols and the shape operator of this inverse surface by the help of these of the tangent developable surface. Morever, we give some necessary and sufficient conditions regarding the inverse surface being flat and minimal. 
M. Evren Aydin and Mahmut Ergut
math.DG