Editing Polar coordinate system (section)

===Conic sections===
A [[conic section]] with one focus on the pole and the other somewhere on the 0° ray (so that the conic's [[semi-major axis|major axis]] lies along the polar axis) is given by:
<math display="block">r = { \ell\over {1 - e \cos \varphi}}</math>
where ''e'' is the [[eccentricity (mathematics)|eccentricity]] and <math>\ell</math> is the [[semi-latus rectum]] (the perpendicular distance at a focus from the major axis to the curve). If {{nowrap|''e'' > 1}}, this equation defines a [[hyperbola]]; if {{math|1=''e'' = 1}}, it defines a [[parabola]]; and if {{math|''e'' < 1}}, it defines an [[ellipse]]. The special case {{math|1=''e'' = 0}} of the latter results in a circle of the radius <math>\ell</math>.
{{Clear}}