[b]Drag around points P00 P20, P22, and P02.[/b][br][br]Improved version of Juan Carlos Ponce Campuzano's [url=https://www.geogebra.org/p/mtgWc2H8cz][b][color=#0000ff]Ellipse[/color][/b][/url][br]That didn't work for horizontal trapezoid, parallelogram, rectangle, etc[br][b][br]Setup[/b][br][br]P00 = (0, 0)[br]P20 = (2, 0)[br]P22 = (2, 2)[br]P02 = (0, 2)[br]square = Polygon({P00, P20, P22, P02})[br]P11 = Intersect(Line(P00, P22), Line(P02, P20))[br]x0 = Line(P00, P02)[br]x2 = Line(P20, P22)[br]x1 = Line(P11, Intersect(x0, x2))[br]y0 = Line(P00, P20)[br]y2 = Line(P02, P22)[br]y1 = Line(P11,Intersect(y0, y2))[br]P10 = Intersect(x1, y0)[br]P21 = Intersect(x2, y1)[br]P12 = Intersect(x1, y2)[br]P01 = Intersect(x0, y1)[br]xy1 = Line(P01, P10)[br]xy3 = Line(P12, P21)[br]xy4 = Line(P22,Intersect(xy3, xy1))[br]P13 = Intersect(x1, xy4)[br]c = Line(P01, P22)[br]c' = Line(P13, P21)[br]C = Intersect(c, c')[br]Ellipse = Conic(P10, P21, C, P12, P01)