What is it about?
Pierre Dandelin constructed a three-dimensional figure and used a simple property concerning circles and tangents to reveal an important property of the ellipse. I show in my piece that the same argument applied to a section through his figure yields relations between a triangle and the circles which may be constructed on its sides.
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Why is it important?
Drawing an analogy across dimensions is a useful heuristic in geometry.
Perspectives
I'm interested in the heuristics, the problem-solving strategies, which may be used in elementary mathematics and, as in this case, publish ideas in the U.K. maths-teaching journals.
Paul Stephenson
Read the Original
This page is a summary of: 101.40 Dandelin circles, The Mathematical Gazette, October 2017, Cambridge University Press,
DOI: 10.1017/mag.2017.142.
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