View source for Iso-optic curve

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A plane curve that is the locus of a vertex of given angle $\gamma$ that moves in the plane in such a way that its sides are tangents to a given curve for all positions of the angle. If $\gamma=\pi/2$, then the iso-optic curve is called an ortho-optic curve. For example, the ortho-optic curve of an ellipse is a circle.

====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  A.A. Savelov,   "Planar curves" , Moscow  (1960)  (In Russian)</TD></TR>
<TR><TD valign="top">[a1]</TD> <TD valign="top">  K. Fladt,   "Analytische Geometrie spezieller Kurven" , Akad. Verlagsgesell.  (1962)</TD></TR><TR><TD valign="top">[a2]</TD> <TD valign="top">  M. Berger,   "Geometry" , '''I''' , Springer  (1987)  pp. 232</TD></TR><TR><TD valign="top">[a3]</TD> <TD valign="top">  M. Berger,   "Geometry" , '''II''' , Springer  (1987)  pp. 239</TD></TR><TR><TD valign="top">[a4]</TD> <TD valign="top">  F.G. Texeira,   "Traité des courbes spéciales remarquables planes on gauches" , Coïmbre  (1908–1915)</TD></TR></table>