Tracing an Ellipse
Date: 08/17/97 at 09:17:15 From: John E Gallo Subject: Ellipse How do you form an ellipse using 3 points?
Date: 08/22/97 at 10:38:15 From: Doctor Rob Subject: Re: Ellipse I think that the procedure to which you are referring is the following. Two of the points are the foci of the ellipse. The third point is a point on the curve. Use a piece of paper. At the foci, put two pins (or tacks, or nails, or whatever). Make a loop of string just long enough to equal the perimeter of the triangle formed by the three points. Put it around the two pins, and put it around your pencil point, which you locate at the third point. It should be taut. Now move the pencil point, keeping the loop taut. It will trace out a curve which is mathematically an ellipse. Here's a picture: F and F' are the foci, and S is the third point. The loop is pictured as the triangle FF'S. -Doctor Rob, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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