Line
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A line is the path of one point moving. A line has length but no width. A line is a type of geometric figure.
A line is made up of an infinite number of points.
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[edit] Line Segments
A line segment is part of a line. An example of a straight line segment:
[edit] Straight and Curved Lines
A line can be straight or curved. The word line usually means a straight line. A straight line is the shortest distance between two points. A straight line is the direction of a point moving in a direction that does not change.
A curved line is sometimes called a curve.
For example, the edge of a circle is not straight. The edge of a circle bends in a curve. Light bends in a curve in air and water, but travels in a straight line away from the earth or other bodies in space where there is no air.
[edit] Naming Lines
Lines can get their names from any two points on the line. For example, if a line has a point named "A" on the line and a point named "B" on the line, then the line can be named either "AB" or "BA".
Sometimes, lines are also named with just one letter; for example, line a could also be recognized as a line on a plane in geometry.
[edit] Two Lines
Two lines can be:
- Parallel: Two lines are parallel if they never meet.
- Concurrent: Two lines are concurrent if they meet in one point.
- Coincident: Two lines are coincident if they are made of the same points.
- Coplanar: Two lines are coplanar if they are in the same plane.
- Perpendicular: Two lines are perpendicular if they form four right angles where they intersect.
- Skew: Two lines are skew if they are not parallel and they never intersect.
