Editing Tri-oval (section)

{{short description|Shape, descriptor of racetracks}}
[[Image:Trioval.svg|thumb|upright=1.5|A tri-oval shape]]
A '''tri-oval''' is a shape which derives its name from the two other shapes it most resembles, a [[triangle]] and an [[Oval (geometry)|oval]].  Rather than meeting at sharp, definable angles as the sides of a triangle do, in a tri-oval these angles are instead rounded into smooth curves.<ref>{{cite web|url=http://www.nascar.com/kyn/101/glossary/index_T_Z.html|title=NASCAR Glossary T-Z|publisher=[[NASCAR]]|access-date=6 December 2009}}</ref>

While an oval has four turns, a tri-oval has six. More formally, according to the [[four-vertex theorem]], every smooth [[simple closed curve]] has at least four [[Vertex (curve)|vertices]], points where its [[curvature]] reaches a local minimum or maximum. In a tri-oval, there are six such points, alternating between three minima and three maxima.