What is a segment. What is a segment? Polygon is a closed broken line

\u003e\u003e Mathematics Grade 7. Full lessons \u003e\u003e Geometry: Cut. Full lessons

Section

The segment is called a part of a straight line, which contains two different points a and b of this straight line (secking ends) and all points direct, which lie between them (internal points of the segment).

Cut straight - This is a set (part of the line) consisting of two different points and all points lying between them. A straight line connecting two points a and b (which are called the sections of the segment) is indicated as follows. If square brackets are lowered in the segment designation, then the "ab" segment is written. Any point lying between the segment ends is called its inner point. The distance between the sections of the segment is called its length and denote as | AB |.

To designate the segment with the ends at the points A and B, we will use the symbol.

On the point C, belonging to the cut AB, it is also said that the point C lies between the points A and B (if C is the inner point of the segment), and also that the cut AB contains the point C.

The properties of the segment is given by the axiom:

Axiom:
Each segment has a certain length, greater zero. The length of the segment is equal to the sum of the lengths of the parts to which it is broken by any of its inner point. AB \u003d AC + CB.

The distance between two points A and B is called length Cut AB.
At the same time, if the points A and B coincide, we assume that the distance between them is zero.
Two segments are called equal, if their lengths are equal.

Section AC \u003d DE, CB \u003d EFand AB \u003d DF.

On the figure 1. Images are depicted A and 3 points on this straight: A, B, C. Point B lies between points a and c, it can be said, it divides points a and c. Points A and C lie on different sides from point B. Points B and C are located one way from point A, points a and b lie one way from point C.

picture 1

Section- Part of a straight line, which consists of all points of this straight, lying between these dots, which are called the sections of the segment. The segment is indicated by the indication of its endpoints. When AB is said, the segment is meant at the ends at the points A and B.

On this figure 2. We see AB cut, it is part of a straight line. The point X lies between the points a and b, so it belongs to the cut of AB, the point Y does not lie between the points A and B, so it does not belong to the AB segment.

figure 2.

The main property of the location of points on a straight line - out of three points on the direct only one lies between two points.

Point A lies between X and Y.

Point X divides the cut AB.

Usually, the segment is not important, in what order its ends are considered: that is, AB and BA segments are the same segment. If the segment is determined direction, that is, the order of transferring it ends, then such a segment is called directional. For example, the above directed segments do not coincide. There is no special designation from the directed segments - the fact that the segment is important to its direction is usually indicated especially.

Further generalization leads to the concept vector- class of all equal in length and coated directional segments.

Crossword

Rides a handle along the sheet. On Lineshke, along the edge. It turns out a damn, called ...
Ancient Greek scientist.
The result of instant touch.
An educational book, consisting of 13 volumes, which for many centuries was the main guidance on geometry.
Ancient Greek scientist, the author of the collective labor "beginning".
Unit of measurement length.
Part of a straight line limited to two dots.
Full length unit in ancient Egypt.
Ancient Greek mathematician who has proven to theorem that carries his name.
Є mathematical sign.
Section geometry.

Interesting fact:

In geometry, the paper is used to: write, draw; cut; bend. The subject of mathematics is so serious that it is useful not to miss the cases to make it a little entertaining.

Circles in the fields - intergalactic language of communication of alien reasonable creatures
Circles on the fields ... how many different opinions, how many ghostas, how much hypotheses, but the intelligible explanation, what it is, does not exist.
Circles on the fields ... They fascinate people with their laconic beauty, they annoy us with incomprehensibility of origin and destination.

Questions:

1) What is a segment?

2) What is the length of the segment?

3) the difference between the segment and the vector?

List of sources used:

Program for general educational institutions. Mathematics. Ministry of Education of the Russian Federation.
Federal Commercial Standard. Bulletin of education. №12,2004.
Programs of general education institutions. Geometry 7-9 classes. Authors: S.A. Burmistra. Moscow. "Enlightenment", 2009.
Kiselev A.P. "Geometry" (planimetry, stereometry)

Edited and expelled Purknak S.A.

The point is an abstract object that does not have measuring characteristics: no height, no length, no radius. In the framework of the task, only its location is important.

The point is indicated by a number or title (large) Latin letter. Several points - different numbers or different letters so that they can be distinguished

point a, point b, point C

A B C.

point 1, point 2, point 3

1 2 3

You can draw three points "A" on a piece of paper and offer a child to spend a line in two points "A". But how to understand through what? A A A.

The line is a variety of points. She is measured only by length. She does not have the widths and thickness

Denotes line (small) Latin letters

line A, line B, line C

A B C.

Line can be

closed if its beginning and end are at one point,
open if its beginning and end are not connected

closed lines

front lines

You got out of the apartment, bought bread in the store and returned back to the apartment. What line turned out? Correctly closed. You returned at the starting point. You got out of the apartment, bought bread in the store, went into the entrance and talked with a neighbor. What line turned out? Front. You did not return at the starting point. You got out of the apartment, bought bread in the store. What line turned out? Front. You did not return at the starting point.

self-playing
without self-integration

self-playing lines

lines without self-sessions

straight
broken
crooked

straight lines

broken lines

curves lines

The straight line is a line that is not curved, has no beginning, no end, it can be continuously continued in both sides

Even when a small plot is visible, it is assumed that it continues endlessly in both directions.

Denotes the line (small) Latin letter. Or two capital (big) latin letters - dots lying on a straight line

straight line A.

straight line AB

B A.

Straight can be

crossing if they have a common point. Two straight lines can intersect only at one point.
- perpendicular if intersect at right angles (90 °).
parallel, if not intersect, do not have a common point.

parallel lines

cross lines

perpendicular lines

Ray is part of the straight line that has the beginning, but does not end, it can be infinitely continued only in one direction

At the beam of light on the picture starting point is the sun

sun

The point shares the straight into two parts - two beams A A

The beam is indicated by a lowercase (small) Latin letter. Or two capital (large) latin letters, where the first is the point with which the beam begins, and the second is the point lying on the beam

beam A.

ray AB

B A.

Rays coincide if

located on the same direct
start at one point
directed one way

the rays of AB and AC coincide

cB and CA rays coincide

C B A.

The segment is a part of a straight line that is limited to two points, that is, it also has the beginning and the end, which means it can be measured its length. The length of the segment is the distance between its initial and endpoints.

After one point you can spend any number of lines, including direct

Two points - an unlimited number of curves, but only one straight

curves lines passing through two points

B A.

straight line AB

B A.

From straight "cut off" a piece and a segment remained. From the example above it can be seen that its length is the poorest distance between two points. ✂ B a ✂

The segment is indicated by two capital (large) Latin letters, where the first is the point with which the segment begins, and the second is the point that the segment ends

cut AB.

B A.

Task: where is the straight, ray, cut, curve?

The broken line is a line consisting of sequentially connected segments not at an angle of 180 °

Long segment "broke" into a few short

Loan links (similar to the links of the chain) are segments from which the broken one is. Related links are links that the end of one level is the beginning of another. Related links should not lie on one straight line.

The vertices of the broken (similar to the vertices of the mountains) is the point with which broken, points in which the segments that form a broken, the point, which ends broken is connected.

It is denoted by the listing of all its vertices.

broken line abcde.

top broken A, Top broken b, Top broken C, Top broken D, Top broken e

lohanned AB, broken BC link, broken CD link, broken de

aB links and bc link are adjacent

bC and CD links are adjacent

cD and DE links are adjacent

A B C D E 64 62 127 52

Length broken - this is the sum of its lengths: abcde \u003d ab + bc + cd + de \u003d 64 + 62 + 127 + 52 \u003d 305

A task: what a broken is longer, but what more peaks? The first line has all the links of the same length, namely, 13cm. The second line has all the links of the same length, namely 49cm. The third line has all the links of the same length, namely 41cm.

Polygon is a closed broken line

The parties of the polygon (help remember the expressions: "Go to all four sides," "Run to the side of the house", "which side can you sit down from?") - It is the links broken. Related sides of a polygon are adjacent links broken.

The tops of the polygon are the peaks of broken. Neighboring vertices are the points of one side of the polygon.

The polygon is denoted by the listing of all its vertices.

closed broken line, not having self-intersections, ABCDEF

polygon abcdef.

the top of the polygon A, the top of the polygon B, the top of the polygon C, the top of the polygon D, the vertex of the polygon E, the top of the polygon F

top A and Top B are adjacent

top B and Top C are adjacent

the vertex C and the vertex D are adjacent

the vertex D and the vertex E are adjacent

the vertex E and the vertex F are adjacent

top F and Top A are adjacent

aB Polygon Side, BC Polygon Side, CD Polygon Side, Cultron Side, Polygon Side, EF Polygon

aB side and BC side are adjacent

bC side and CD side are adjacent

side CD and side DE are adjacent

face DE and EF side are adjacent

eF side and FA side are adjacent

A B C D E F 120 60 58 122 98 141

The perimeter of the polygon is the length of broken: P \u003d AB + BC + CD + DE + EF + FA \u003d 120 + 60 + 58 + 122 + 98 + 141 \u003d 599

The polygon with three vertices is called a triangle, with a four-four-trigger, with five - pentagon, etc.

Section. Cut length. Triangle.

1. In this paragraph you will get acquainted with some concepts of geometry. Geometry- Science of "Measurement of Earth". This word comes from Latin words: GEO - Earth and Metr - Measure, measure. In geometry are studied different geometric objects, their properties, their connections with the outside world. The simplest geometric objects are a point, line, surface. More complex geometric objects, for example, geometric shapes and bodies, are formed from the simplest.

If you attach to two points A and in the ruler and along it to spend a line connecting these points, then we will get section, which is called AV or VA (read: "A - BE", "BE- A"). Points a and c called segments of cut (picture 1). The distance between the sections of the segment, measured in units of length, is called lena Cutka.

Units of length: M - meter, cm - centimeter, dm - decimeter, mm - millimeter, km - kilometer, etc. (1 km \u003d 1000 m; 1m \u003d 10 dm; 1 dm \u003d 10 cm; 1 cm \u003d 10 mm).To measure the length of the segments use a rulette, roulette. Measure the length of the segment, it means to find out how many times one or another length is stacked in it.

Equal Two segments are called, which can be combined by imposing one to another (Figure 2). For example, you can cut in real or mentally one of the segments and attach to another so that their ends coincided. If the segments of AB and SC are equal, then they write AB \u003d SC. Equal segments have equal lengths. It is true: two segments that have equal lengths are equal. If two segments have different lengths, then they are not equal. Of the two unequal segments, the one that is part of the other segment is. You can compare segments by overlay using a circuit.

If you mentally extend the segment AB in both sides to infinity, then we will receive an idea of straight AB (Figure 3). Any point lying on a straight line breaks it into two ray(Figure 4). Point with breaks straight AB for two ray Sa and St. Tosca C called the beginning of the beam.

2. If three points that are not lying on one straight line, connect the segments, then we get a figure called triangle.Data points are called verters triangle, and segments that connect them, parties Triangle (Figure 5). Fnm is a triangle, segments Fn, Nm, Fm - triangle sides, points F, N, M - triangle vertices. The sides of all triangles have the following property: lina any of the sides of the triangle is always less than the sum of the length of the other two of its sides.

If you mentally extend in all directions, for example, the surface of the table lid, then we get an idea of plane. Points, segments, straight, rays are located on the plane (Figure 6).

Block 1. Additional

The world in which we live, all that surrounds us, ancient called nature or space. The space in which we live is considered three-dimensional, i.e. It has three dimensions. They are often called: length, width and height (for example, room length 4 m, room width 2 m and height 3 m).

The idea of \u200b\u200bthe geometric (mathematical) point gives us a star at the night sky, the point at the end of this sentence, a track from the needle, etc. However, all listed objects have dimensions, in contrast to them, the dimensions of the geometric point are considered to be zero (its measurements are zero). Therefore, a real mathematical point can only be mentally submitted. You can also say where it is located. Putting the point in the notebook to the notebook, we will not depict a geometric point, but we assume that the constructed object is a geometric point (Figure 6). The points are denoted by capital letters of the Latin alphabet: A., B., C., D., (read " point A, point BE, Point CE, point DE ") (Figure 7).

Wires hanging on the pillars, the visible line of the horizon (the border between the sky and the earth or water), the river bed, depicted on the map, the gymnastic hoop, the water jet, beating from the fountain give us an idea of \u200b\u200bthe lines.

There are closed and unlocked lines, smooth and non-smooth lines, lines with self-intersection and without self-integer (Figures 8 and 9).

Sheet of paper, laser disk, soccer ball shell, packaging box cardboard, New Year's plastic mask, etc. give us an idea of surfaces(Figure 10). When the floor is painted or car, then the paint is the surface of the floor or car.

Human body, stone, brick, cheese head, ball, ice icicle, etc. give us an idea of geometricbodies (Figure 11).

The most simple of all lines - this is straight. We put a lineup to a sheet of paper and carry a pencil along it a direct line. Mentally continuing this line to infinity in both directions, we will receive an idea of \u200b\u200ba straight line. It is believed that direct has one dimension - length, and the other two of its measurements are zero (Figure 12).

When solving problems, the direct is depicted in the form of a line, which is carried out along the line of the pencil or chalk. Direct are indicated by the line latin letters: a, b, n, m (Figure 13). It can be denoted directly by two letters corresponding to the points lying on it. For example, straight n. In Figure 13, you can designate: Av or va, andD. orD.BUT,D.In or inD..

Points can lie on a straight line (belong to direct) and do not lie on a straight line (do not belong to the line). Figure 13 shows the points A, D, B, lying on a straight AB (direct AB owned by direct AB). At the same time they write. Read: Point A is a direct AB, the point B belongs to AB, the point D belongs to AV. Point D also belongs direct M, it is called general Point. At point D, straight AB and M intersect. Points P and R do not belong to direct AB and M:

Through any two points always you can spend direct and only one .

Of all types of lines connecting any two points, the smallest length has a segment, the ends of which are the points of the point (Figure 14).

The figure that consists of points and connecting their segments is called a broken (Figure 15). Segments forming broken, are called links broken, and their ends - vertersbroken. Called (denoted) a broken, listed in order all its vertices, for example, a broken abcdefg. The length of the broken is called the sum of its lengths of its links. So, the length of the broken abcdefg is equal to the sum: AB + BC + CD + DE + EF + FG.

Closed scrap called polygon, her vertices are called tops of a polygonand her links parties polygon (Figure 16). Called (denoted) a polygon, listed in order all its vertices, starting with any, for example, a polygon (sevenfone) ABCDEFG, polygon (pentagon) RTPKL:

The sum of the lengths of all sides of the polygon is called perimeter polygon and designated Latin letterp. (Read: pE). The perimeters of polygons in Figure 13:

P abcdefg \u003d ab + Bc + CD + DE + EF + FG + GA.

P RTPKL \u003d RT + TP + PK + KL + LR.

Mentally extended the surface of the table cover or window glass to infinity in all directions, we get an idea of \u200b\u200bthe surface called plane (Figure 17). Denote planes with small letters of the Greek alphabet: α, β, γ, δ, ... (read: alpha, Betta, Gamma, Delta, etc. plane, etc.).

Block 2. Dictionary.

Make a dictionary of new terms and definitions from §2. To do this, in the empty rows of the table, enter the words from the list of terms below. Table 2 Specify terms of terms according to row numbers. It is recommended before filling in the dictionary to once again look at §2 and block 2.1.

Block 3. Install the correspondence (USA).

Geometric figures.

Block 4. Self-test.

Segment measurement using a ruler.

Recall that to measure the segment of AB in centimeters, it means to compare it with a length of 1 cm and find out how many of these segments 1cm is placed in the segment of AV. To measure the segment in other lengths of length, come in a similar way.

To perform tasks, work according to the plan shown in the left column of the table. At the same time, the right column is recommended to close the paper sheet. Then you can compare your conclusions with solutions given in the table on the right.

Block 5. Establish a sequence of actions (UE).

Constructing a segment of a given length.

Option 1. The table recorded a confused algorithm (confused procedure) of constructing a segment of a given length (for example, we construct a segment of the aircraft \u003d 7cm). In the left column, indicating the action in the right the result of this action. Rearrange the rows of the table so that the correct algorithm for constructing a segment of a given length is obtained. Write down the correct sequence of actions.

Option 2. The following table shows an algorithm for constructing a CM \u003d N cm, where instead n. You can substitute any number. In this embodiment, there is no match between action and result. Therefore, it is necessary to set a sequence of actions, then for each action to select its result. Answer write in the form: 2a, 1B, 4B, etc.

Option 3. Using the algorithm of option 2, build a segment in the notebook with n \u003d 3 cm, n \u003d 10 cm, n \u003d 12 cm.

Block 6. FACE TEST.

Cut, ray, straight, plane.

In the tasks of the facade test, pictures and recordings are used below the numbers 1 - 12, given in Table 1. Of these, these tasks are formed. Then the requirements of the tasks are added to them, which in the test are placed after the connecting word "that". Answers to tasks are placed after the word "equal." The task set is shown in Table 2. For example, the task 6.15.19 is drawn up as follows: "If the task uses Figure 6 , Z.the condition is added to it under number 15, the requirement of the task is under the number 19. "

13) to build four points so that every three of them did not lie on one straight line;

14) spend every two point direct;

15) Each of the surfaces of the box to extend mentally in all directions to infinity;

16) the number of different segments in the figure;

17) the number of different rays in the figure;

18) the number of different straight lines in the figure;

19) the number of different planes;

20) Cut length length in centimeters;

21) Cut length AB in kilometers;

22) DC segment length in meters;

23) PRQ triangle perimeter;

24) QPRMN broken length;

25) Private perimeters of RMN and PRQ triangles;

26) Cut length ED;

27) Cut length BE;

28) the number of times the intersection of direct;

29) the number of obtained triangles;

30) the number of parts to which the plane was divided;

31) the perimeter of the polygon, expressed in meters;

32) the perimeter of the polygon, expressed in decimeters;

33) the perimeter of the polygon, expressed in centimeters;

34) the perimeter of the polygon, expressed in millimeters;

35) the perimeter of the polygon, expressed in kilometers;

Equally (equal, has the appearance):

a) 70; b) 4; c) 217; d) 8; e) 20; e) 10; g) 8 ∙ b; h) 800 ∙ B; and) 8000 ∙ B; k) 80 ∙ b; l) 63000; m) 63; H) 63000000; o) 3; n) 6; p) 630000; c) 6300000; T) 7; y) 5; f) 22; x) 28.

Block 7. Let's play.

7.1. Mathematical labyrinth.

The labyrinth consists of ten rooms with three doors each. Each of the rooms is one of the geometric object (it is drawn on the wall of the room). Information about this object is in the "guidebook" in the labyrinth. Reading him, you need to move into the room that is written in the guidebook. Passing through the rooms of the labyrinth, draw your route. In the last two rooms there are outputs.

Labyrinth guidebook

Log in the labyrinth It is necessary through the room where the geometric object is located, which has no beginning, but there are two ends.
The geometric object of this room does not have the sizes, he is like a distant star at the night sky.
The geometric object of this room is made up of four segments having three common points.
This geometric object consists of four segments with four common points.
In this room there are geometric objects, each of which has the beginning, but does not end.
Here are two geometric objects that do not have any beginning, no end, but with one common point.

The idea of \u200b\u200bthis geometric object gives flight of artillery shells

(Trajectory of movement).

In this room there is a geometric object with three vertices, but it is not a mountain

This geometric object gives the flight of a boomeranga (hunting

australian indigenous weapons). In physics, this line is called the trajectory

body movement.

The idea of \u200b\u200bthis geometric object gives the surface of the lake in

clear weather.

Now you can leave the labyrinth.

In the maze there are geometric objects: plane, open line, straight, triangle, point, closed line, broken, cut, ray, quadricle.

7.2. Perimeter of geometric shapes.

In the drawings, highlight geometric shapes: triangles, quadricles, five - and hexagons. Using the line (in millimeters), determine the perimeters of some of them.

7.3. Relay of geometric objects.

In the tasks, the relay has an empty framework. Put the missed word in them. Then transfer this word to another frame where the arrow shows. In this case, you can change the case of this word. Passing the stages of the relay, perform the required constructions. If the baton is passing correctly, then at the end you will receive the word: perimeter.

7.4. Fortress of geometric objects.

Read § 2, write out the name of the geometric objects from its text. Then enter these words into the empty cells of the Fortress.

Hello, dear blog readers Website. One of the concepts of geometry, with which they get acquainted in elementary school, is a segment. The um tasks in mathematics and geometry is built on the concepts of segment and direct.

Understanding what segment is help to solve all sorts of tasks and examples in mathematics lessons in both school and in higher educational institutions.

Cut is a geometric figure

According to the definition in the dictionary, the segment is called part of directlimited to two points on it. It is according to the designations of these points and the name of the segment is given.

The figure shown below shows the AB cut. Points a and b are the ends of the segment. The length of the segment is called the distance between its ends.

In mathematics, it is customary to denote the points, and correspondingly segments, large letters of the Latin alphabet. If you need to draw a segment, most often it is depicted without direct, but only from one end to the other.

It can also be said that the segment - this is a totality of all pointswhich lie on one straight and are between two predetermined points that are the ends of this segment.

If you mark another point on the segment between its ends, it will split this segment for two. The length of the segment AB can be calculated by losing the length of the segments of the AU and SV.

The difference between the segment, the beam and direct

Schoolchildren sometimes confuse the concepts of straight, ray and segment. Indeed, these concepts are very similar to each other, but they have a fundamental difference:

Straight It is called a line that is not curved, and also does not start and end.
Ray - This is a part of a straight line limited to one point. It has the beginning and has no end.
limited to two points. It has both the beginning and the end.

The point on the line divides it into two beams. The number of segments on one straight can be infinite.

To distinguish between these figures in the figure, at the beginning and end of the drawd line are set or not set. Drawing a ray, the point is put at one end, and the segment of the segment is in both ends. Straight does not have ends, so the points at the end of the line are not set.

Directed segment is a vector

Segments are two types:

Unpaired.
Directed.

For non-directional segments, AB and VA are the same segments, since the direction does not matter.

If we talk about directed segments, the order of transferring its ends is crucial. In this case, AB ➜ and VA ➜ are different segments, as they are oppositely directed.

Directional segments called vectors. Vectors can be designated as two capital letters of the Latin alphabet with the arrow above them and one small letter with the arrow.

The vector module is called the length of the directional segment. Denotes as av ➜. Modules of vectors av ➜ and va ➜ are equal.

Vectors are often considered in the coordinate system. Vector module is equal to square root square coordinate vector coordinates.

Collinear vectors are called those that lie on one or on parallel straight lines.

The broken line is a set of connected segments.

The broken line consists of a plurality of segments that are called its links. These segments are connected to each other with their ends and are not located at an angle of 180 °.

The peaks of the broken are the following points:

The point with which the broken has begun.
The point that the broken ended.
Points in which adjacent links are connected (cuts of broken).

The number of premium vertices is always one more than the number of its links. It is denoted by the lunch of all its vertices from one end and ending with others.

For example, the broken ABCDEF consists of segments of AB, BC, CD, DE and EF and the vertices of A, B, C, D, E and F. AB and BC links are adjacent, since they have a total end - point V. Length of the broken is calculated as The sum of the lengths of all its links.

Any closed broken is a geometric figure - a polygon.

The sum of the angles of the polygon is multiple 180 ° and is calculated according to the following formula 180 * (N-2), where N is the number of angles or segments that make up this figure.

Time interval

Interestingly, the word segment is applicable not only to geometric concepts, but also as a temporary term.

The period of time is called the period between two events, dates. It can be measured as seconds or minutes, as well as years or even decades.

Time as a whole in this case is defined as temporary straight.

Good luck to you! To ambiguous meetings on the blog pages Website

Point in mathematics

What is a point in mathematics? The mathematical point does not matter and denotes the title Latin letters: a, b, c, d, f, etc.

In the figure you can see the image of the points A, B, C, D, F, E, M, T, S.

Cut in mathematics

What is a segment in mathematics? In mathematics lessons, you can hear the following explanation: the mathematical segment has a length and ends. The segment in mathematics is a totality of all points lying on a straight line between the sections of the segment. Cuts segment - two border points.

In the figure, we see the following: segments ,,,, and, as well as two points B and S.

Straight in mathematics

What is a straight line in mathematics? Definition direct in mathematics: Straight does not ends and can continue in both sides to infinity. A straight line in mathematics is indicated by two any dots direct. To explain the concept of a direct student, we can say that direct is a segment that does not have two ends.

The figure shows two direct: CD and EF.

Bump in mathematics

What is the beam? Definition of the beam in mathematics: the beam is part of the straight, which has the beginning and has no end. In the title of the beam there are two letters, for example, DC. Moreover, the first letter always denotes the point of the start of the beam, so let the letters cannot be changed.

The figure shows the rays: DC, KC, EF, MT, MS. Rays KC and KD - one beam, because They have a common start.

Numerical straight in mathematics

The definition of a numerical straight in mathematics: straight, points of which marked numbers, called a numeric line.

The figure shows the numerical straight, as well as the beam OD and ED