Euclidean plane

	Main Article	Discussion	Related Articles  [?]	Bibliography  [?]	External Links  [?]	Citable Version  [?]
	This editable Main Article is under development and subject to a disclaimer. [edit intro]

The Euclidean plane is the plane that is the object of study in Euclidean geometry (high-school geometry). The plane and the geometry are named after the ancient-Greek mathematician Euclid.

The Euclidean plane is a collection of points P, Q, R, ... between which a distance ρ is defined, with the properties,

1. ρ(P,Q) ≥ 0 and ρ(P,Q) = 0 if and only if P = Q
2. ρ(P,Q) = ρ(Q,P)
3. ρ(P,Q) ≤ ρ(P,R) + ρ(R,Q) (triangular inequality).

As is known from Euclidean geometry lines can be drawn between points and different geometric figures (triangles, squares, etc.) can be constructed. A geometric figure can be translated and rotated without change of shape. Such a map is called a rigid motion of the figure. The totality of rigid motions form a group of infinite order, the Euclidean group in two dimensions, often written as E(2).

Formally, the Euclidean plane is a 2-dimensional affine space with inner product.