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November 15th, 2010, 01:28 PM  #1 
Senior Member Joined: Apr 2009 Posts: 106 Thanks: 0  Parabola and Directrix and Focus, Oh MY!!!
For the parabola y = x^2 I have determined that the focus is the point (0, 1/4) I have determined that the directrix is the line y = 1/4 Am I correct? 
November 15th, 2010, 01:48 PM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: Parabola and Directrix and Focus, Oh MY!!!
Yes, that is correct. For the parabola whose axis of symmetry is the yaxis and whose vertex is at the origin,i.e the focus will be at and the directrix will be the line , which can be found using the definition of the parabola, i.e., the locus of all points being equidistant from a fixed line, the directrix, and a fixed point not on the line, the focus. 
February 21st, 2013, 09:00 PM  #3  
Banned Camp Joined: Feb 2013 Posts: 224 Thanks: 6  Re: Parabola and Directrix and Focus, Oh MY!!! Quote:
http://www.flickr.com/photos/85937466@N ... hotostream or this http://quadrivium.info/GGB/ParabRhombus.html  

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