A line is a set of points. Geometrically, it is represented as a straight line, that is, it does not curve at all.
It is possible to imagine that a set with two points forms a line, however, there is a result that states that a straight line has infinite points and also a postulate that says: Given two points, there is a single line that contains them.. Therefore, lines can be “drawn” from just two points, however, they are infinite in both the direction of the first point and the direction of the second.
Considering that the lines have infinite points, it is concluded that they also have infinite length. In the example below, if we continued drawing the line in any of its directions, we would never finish, as the line is infinite.
Line r, which contains points A and B, represented in the Cartesian plane
What are Semi-Straights?
Semi-straights, in turn, are similar to "half of the line". The ray lines are constructed as follows: Considering two points A and B on the plane, draw the line that contains them. After that, choose one of the two points (A, for example) and make a cut on the straight line. Thus, we will have two straight lines, one starting at A and following the direction of B and the other in the opposite direction. In other words, d
from the colon A and B, the semi-straight from A and towards B is a part of the line that contains points A and B starting at A.
Semi-rectal of origin in A with direction B
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What is a straight segment?
straight segmentit is a set of points that includes the distinct points A and B and the straight line between them. In this way, a straight line segment can be built, following the strategy used to build a semi-straight line, as follows way: Given two points A and B on the plane and considering the line that contains them, make two cuts on it, one over point A and one over the point B. The finite part of the line between points A and B is line segment AB.
Example of straight line segment AB, after two cuts in a straight line
Points and Line Segments
In Spatial Geometry and, consequently, in the plane, points are understood as objects without definition, without dimension, without shape, but representing a unique location in space.
It is possible to accurately calculate the distance between two points. This distance describes a straight segment. If the point had a shape, it would be possible for this distance to vary a little depending on where the measurement was taken at the point. If the point had a dimension, this distance would vary greatly, as the end of the straight line that touches this point could be anywhere in the dimension defined by it.
Thus, two different locations imply two different points. If two points are located at the same location, then it is a single point.
By Luiz Paulo Moreira
Graduated in Mathematics
Would you like to reference this text in a school or academic work? Look:
SILVA, Luiz Paulo Moreira. "What is straight?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/matematica/o-que-e-reta.htm. Accessed on June 27, 2021.
