Da Vinci's Construction of an Ellipse

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As vertex of triangle
slides along the horizontal axis, vertex
slides along the other axis, which does not have to be perpendicular. Vertex
then traces out the arc of an ellipse. There can be two solutions for
.
Contributed by: Borut Levart (April 2014)
Open content licensed under CC BY-NC-SA
Snapshots
Details
Two locators control the position of vertex and the axis angle. You can vary the triangle sides
and
and the angle
at vertex
with the slider controls.
This method of drawing an ellipse was found by Leonardo da Vinci.
Reference
[1] D. Wells, The Penguin Dictionary of Curious and Interesting Geometry, London: Penguin, 1991.
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