An Integral Formula Related to Inner Isoptics

  • Horst Martini

    Technische Universität Chemnitz, Germany
  • Witold Mozgawa

    Uniwersytet Marii Curie-Skłodowskiej, Lublin, Poland


An isoptic of a strictly convex -curve in the plane is the locus of all points from which is seen under the same fixed angle. The two supporting lines of through such a point determine a secant of , and the envelope of all these secants is the inner isoptic of and . We describe an integral formula for inner isoptics in terms of quantities that naturally occur in this geometric configuration.

Cite this article

Horst Martini, Witold Mozgawa, An Integral Formula Related to Inner Isoptics. Rend. Sem. Mat. Univ. Padova 125 (2011), pp. 39–49

DOI 10.4171/RSMUP/125-3