Talk:Plane (geometry)/Archive 1

Picture

Sorry, again. But this is even more a bad idea! This picture may -- perhaps! -- be used to illustrate the topological concept of a surface, certainly not that of a plane. --Peter Schmitt 00:42, 18 March 2010 (UTC)

Remarks

"A plane is a surface on which a line perpendicular to a line which lies on that surface also falls entirely on the surface" — where is it taken from?? Hopelessly bad "definition".

"A plane is made up of an infinite number of straight lines" — it surely contains infinitely many straight lines, as well as infinitely many triangles, circles etc. But is it "made up" of them??

"Surfaces can be parallel" — really? what is the definition of this notion?

"Thus the surface has on it point A, point B, and point C is called surface ABC" — a plane is determined by three points (if not on a straight line), but a surface is not.

"If this crumpled picture of the Earth was spread flat on a perfectly flat table, and the picture had absolutely no thickness, then it would be a plane" — no, it would be a finite domain on a plane.

Boris Tsirelson 15:29, 28 March 2010 (UTC)

Rewritten

I was bold enough to rewrite it completely. Hope you do not object. Could someone please add an appropriate lead, and probably introduction with a completely informal idea of plane? It would be also nice to have pictures to the three geometric definitions. Boris Tsirelson 09:57, 29 March 2010 (UTC)

Analytic geometry

I added some high-school-level analytic geometry plus two drawings. --Paul Wormer 10:46, 1 April 2010 (UTC)