# The foci of an ellipse, reflected across its tangents

James Tanton asked: Reflect an

**ellipse**across each**tangent line**to it. What curve(s) do the images of its two foci trace? The**ellipse**shown below can be modified by dragging the three**red points**. The**tangent line**can be chosen by dragging the**blue point**. The reflections of the foci, and the curves they trace, are shown in green and purple.## New Resources

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