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Unions of Sets Starshaped via Staircase Paths or via Paths of Bounded Length
Authors:Marilyn Breen
Affiliation:(1) Department of Mathematics, University of Oklahoma, 601 Elm Avenue, Norman, OK, 73019-0315, U.S.A.
Abstract:Let S be an orthogonal polygon in the plane, S simply connected, and let k=2,3. Set S is a union of k sets starshaped via staircase paths if and only if for every F finite, F
$$subseteq$$
bdry S, there is a set G
$$subseteq$$
bdry S arbitrarily close to F and points si,1 le ilek, (depending on G) such that each point of G is clearly visible from some si. An analogous result holds for a union of 2 sets starshaped via agr-paths when S is a closed simply connected set in the plane. Each result is best possible.
Keywords:unions of starshaped sets  staircase paths    /content/t708224504t8pq67/xxlarge945.gif"   alt="  agr"   align="  BASELINE"   BORDER="  0"  >-paths.
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