Constructing an Ellipse: Geometric Construction with Circles and Lines (M. Tsilp

① This GeoGebra example demonstrates how to construct an ellipse step-by-step using circles, lines, and their intersections, revealing the geometric relationship behind the conic. ② Core mathematical concepts include the definition of an ellipse (sum of distances to two foci is constant), circle intersection and tangency, perpendicular lines, midpoints, distance measurement, and ratios used in the construction. ③ Construction highlights: based on the summary, the commands used are Circle, Intersect, Ellipse, Line, Point, Segment, Midpoint, OrthogonalLine, and Distance, involving objects such as points, segments, circles, auxiliary lines, and text labels. The construction integrates dynamic geometry to produce the ellipse from basic elements. ④ Suitable for high school or college analytic geometry courses, this example helps students understand the connection between ellipses, circles, and lines, and serves as a teaching demonstration for geometric construction of conic sections.