*World of Mathematics*. ©2005-2006 Thomson Gale, a part of the Thomson Corporation. All rights reserved.

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## Plane Geometry

Plane **geometry** is that subsection of geometry that deals with figures in a two-dimensional plane. Euclidean geometry, sometimes called parabolic geometry, is divided into two subsections: plane geometry, geometry dealing with figures in a plane, and **solid geometry**, geometry dealing with solid in three-dimensional **space**. Plane geometry is sometimes called two-dimensional Euclidean geometry and deals with figures such as circles, lines, **polygons** and the like. Plane geometry is concerned with the study of figures in two-dimensional Euclidean space, which is usually denoted **R**^{2}, also known as the Euclidean plane. This branch of Euclidean geometry is also focused on studying the properties of flat surfaces.

Plane geometry is a branch of Euclidean geometry, developed by Greek mathematician Euclid in the 4th century B.C., that is governed by Euclid's five postulates as laid out in his work *The Elements*. In the early 20th century mathematicians recognized that...

This section contains 533 words(approx. 2 pages at 300 words per page) |