Oval (geometry)
From Freepedia
In geometry, an oval or ovoid (from Latin ovum, 'egg') is any curve resembling a cross-section of a chicken egg or the outline of a speed skating track. Unlike other curves, the term 'oval' is not well-defined and many distinct curves are commonly called ovals. These curves have in common that:
- they are differentiable (smooth-looking), simple (not self-intersecting), closed, plane curves;
- their shape does not depart too much from that of a circle or an ellipse, and
- there is at least one axis of symmetry.
The circle and the ellipse fit these criteria, but are rarely called 'ovals' because the terms 'circle' and 'ellipse' are better known, more specific and well-defined. Two examples of ovals are shown below. In (a), a semicircle is joined to half an ellipse while in (b), two semicircles are connected with straight line segments. Other ad hoc constructions are often encountered as well.
| Image:Oval1.PNG | Image:Oval2.PNG |
| (a) Chicken egg | (b) Speed skating track |
Egg shape
The shape of an egg is approximately an oblate ellipsoid, but, while keeping cylindrical symmetry, as illustrated above, there is not quite symmetry in a plane perpendicular to the long axis. The term egg-shaped is typically used taking this asymmetry into account, but it may also simply mean oblate ellipsoid. It can also be used for a 2D shape.
