@article {MATHEDUC.06495941,
author = {Berendonk, Stephan},
title = {Stretched circles are conic sections, a geometric proof.},
year = {2014},
journal = {The College Mathematics Journal},
volume = {45},
number = {4},
issn = {0746-8342},
pages = {316-317},
publisher = {Mathematical Association of America (MAA), Washington, D.C.},
doi = {10.4169/college.math.j.45.4.316},
abstract = {Summary: We give a geometric proof for the fact that a conic section, if it is a closed curve, satisfies the equation of an ellipse.},
msc2010 = {G75xx (G45xx)},
identifier = {2015f.00735},
}