undefined Terms sdrta.net Topical overview | Geometry outline | MathBits" Teacher resources Terms the Use call Person: Donna Roberts
In geometry, formal definitions are formed using other identified words or terms. Over there are, however, three words in geometry that space not officially defined. This words are point, line and also plane, and also are referred to as the "three undefined terms of geometry".
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While this words room "undefined" in the formal sense, we deserve to still "describe" these words. The descriptions, declared below, refer to these words in relationship to geometry.
POINT • a allude indicates a location (or position) in space. • a point has no dimension (actual size). • a point has no length, no width, and also no height (thickness). • a suggest is usually named with a capital letter. • in the coordinate plane, a point is named by an notified pair, (x,y). if we represent a suggest with a dot, the dot have the right to be an extremely tiny or very large. Remember, a point has no size.
The size of the dot drawn to represent a allude makes no difference. Points have no size. They simply represent a location.
LINE (straight line) • a line has no thickness. • a line"s size extends in one dimension. • a heat goes on forever in both directions. • a line has infinite length, zero width, and zero height. • a line is presume to it is in straight. • a line is drawn with arrowheads on both ends. • a line is named by a single lowercase script letter, or by any kind of two (or more) points i m sorry lie top top the line.
Lines deserve to be labeled v a solitary script letter, or by 2 points top top the line,
. The thickness of a line makes no difference.
See more: “ Broadening Your Perspective 5-2, Broadening Your Perspective 5
PLANE • a plane has two dimensions. • a plane forms a level surface extending indefinitely in all directions. • a airplane has boundless length, infinite width and also zero elevation (thickness). • a plane is attracted as a four-sided figure resembling a table or a parallelogram. • a aircraft is named by a solitary letter (plane m) or by three coplanar, yet non-collinear,* clues (plane ABC).
airplane m or aircraft ABC. When the diagram of a airplane has edges, you have to remember that the aircraft actually has actually no boundaries.
* collinear points are points the lie top top the exact same straight line. Coplanar points are points the line in the very same plane.