$\alpha$-isoptics of a triangle and their connection to $\alpha$-isoptic of an oval

Abstract

For a fixed positive angle $\alpha$, $\alpha <\pi$ we get an explicit formulas for an $\alpha$-isoptic curve of a triangle and study some of its properties. We use obtained results to show that $\alpha$-isoptic of an oval is an envelope of $\alpha$-isoptics of properly chosen triangles.