Geometry and Trigonometry

Plane Geometry

What does a “plane” mean in geometry?

A plane—in geometry or any other field of mathematics—means a surface such that a straight line joining any two of its points lies totally in that surface. A plane is considered to be two-dimensional; when a plane is discussed with higher dimensions, it is called a hyperplane. Thus, in the majority of mathematical discussions, a plane can be thought of as a two-dimensional group of points that reach out to infinity in all directions (for more information about dimensions, see above).


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