Line (geometry)
A line is the path of one point that is moving. A line is a type of geometric figure. A line has length, but no width. A line is made up of an endless number of points.
Straight and curved lines
A line can be straight or curved. In geometry, the word line means a straight line. A straight line is the shortest distance between two points. A straight line is traced by a point moving in a direction that does not change.
A curved line is sometimes called a curve. The edge of a circle is not straight. It is an example of a curve.
Line segments
A line segment is part of a line. Here are examples of straight line segments:
- _____ __
Naming lines
Lines can get their names from any two points on the line. For example, if a line contains two different points, named [math]\displaystyle{ A }[/math] and [math]\displaystyle{ B }[/math], then the line can be called either [math]\displaystyle{ \overleftrightarrow{AB} }[/math], or [math]\displaystyle{ \overleftrightarrow{BA} }[/math].
Sometimes, lines are named with just one symbol. A letter such as [math]\displaystyle{ \ell }[/math] might be used.[1][2][3]
Two lines
Two lines can be:
- Parallel: Two lines are parallel if they are on the same plane and they never touch.
- Concurrent: Two lines are concurrent if they touch on one point.
- Coincident: Two lines are coincident if they are made of the same points.
- Perpendicular: Two lines are perpendicular if they make four right angles where they touch.
- Skew: In Euclidean space, two lines are skew if they are not parallel but they never touch.
Line (geometry) Media
A red line near the origin on the two-dimensional Cartesian coordinate system
Tangent to a curve. The red line is tangential to the curve at the point marked by a red dot.
Line graphs of linear equations on the Cartesian plane
Distance from the origin O to the line E calculated with the Hesse normal form. Normal vector in red, line in green, point O shown in blue.
A line on polar coordinates without passing though the origin, with the general parametric equation written above
A great circle divides the sphere in two equal hemispheres, while also satisfying the "no curvature" property.
- Ray(A,B,C)
Drawing of a line segment "AB" on the line "a"
Number line with numbers from -3 to 3 and two drawed numbers x and y with x < y.
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Related pages
References
- ↑ "Compendium of Mathematical Symbols". Math Vault. 2020-03-01. Retrieved 2020-08-16.
- ↑ Weisstein, Eric W. "Line". mathworld.wolfram.com. Retrieved 2020-08-16.
- ↑ "An introduction to geometry (Geometry, Points, Lines, Planes and Angles)". Mathplanet. Archived from the original on 2020-09-29. Retrieved 2020-08-16.