Visual Illusion: Isosceles Triangles with Fixed Perimeter Tracing an Ellipse

This GeoGebra example demonstrates a visual illusion where the apexes of isosceles triangles with a fixed perimeter trace out an ellipse. It explores key mathematical concepts including inequalities (to constrain side lengths), properties of isosceles triangles, constant perimeter conditions, and the geometric definition of an ellipse as a locus. The construction uses the Sequence command to generate a family of triangles parameterized by variable k, with lines l1 and l2 serving as symmetry axes or boundary constraints. Ideal for high school mathematics instruction, this model supports inquiry-based learning in coordinate geometry, locus problems, and geometric inequalities.