Along with such concepts as point, segment, line, there is one more concept in geometry. It is called ray. A ray is a part of a straight line, limited on one side by a point, and on the other side - infinite, i.e. not limited by anything.
An analogy can be drawn with nature. For example, a beam of light that we can direct from earth into space. On the one hand it is limited, but on the other hand it is not. Each beam has one extreme point, in which it begins. It's called the beginning of the ray.
If we take an arbitrary straight line a, and mark some point on it ABOUT, then this point will split our line into two parts. Each of which will be a ray. Point O will belong to each of these rays. Point O will be at in this case the beginning of these two rays.
The beam is usually designated by one Latin letter. The figure below shows ray k.
You can also denote the beam with two capital Latin letters. In this case, the first of them is the point at which the beginning of the beam lies. The second is the point that belongs to the ray, or in other words, through which the ray passes.
The figure shows the OS beam.
Another way to designate a ray is to indicate the starting point of the ray and the line to which this ray belongs. For example, the figure below shows the ray Ok.
Sometimes they say that the ray comes from point O. This means that point O is the beginning of the ray. Rays are also sometimes called semi-straight.
Task:
Draw a straight line and mark points A B on it and mark point C on segment AB. Among the rays AB, BC, CA, AC and BA, find pairs of coinciding rays.
The rays coincide if they lie on the same straight line and have general beginning and none of them is a continuation of another ray.
The figure shows that these conditions are met by rays AB and AC, as well as rays BC and BA. Therefore, they are coincident.
Despite the fact that geometry is one of the exact sciences, scientists cannot unambiguously define the term “straight”. In the very general view we can give the following definition: “A straight line is a line along which equal to the distance between two points."
What is a straight line in mathematics? The definition of a straight line in mathematics is that a straight line has no ends and can continue in both directions indefinitely.
The basic concepts of geometry include point, line and plane; they are given without definition, but definitions of other geometric figures are given through these concepts. A plane, like a straight line, is a primary concept that has no definition. This statement is established by the following axiom: if two points of a line lie in a certain plane, then all points of this line lie in this plane. And the statement itself that is being proven is called a theorem. The formulation of the theorem usually consists of two parts.
Problem: where is the line, ray, segment, curve? The vertices of a broken line (similar to the tops of mountains) are the point from which the broken line begins, the points at which the segments that form the broken line are connected, the point at which the broken line ends. Problem: which broken line is longer and which has more vertices? Adjacent sides polygon is adjacent links broken. The vertices of a polygon are the vertices of a broken line. Adjacent vertices are the endpoints of one side of the polygon.
In mathematics lessons you can hear the following explanation: a mathematical segment has a length and ends. A segment in mathematics is the set of all points lying on a straight line between the ends of the segment.
In what follows there will be definitions for different figures except two - a point and a straight line. This means that sometimes we can denote a straight line with two large in Latin letters, for example, line \(AB\), since no other line can be drawn through these two points. Symbolically we write the segment \(AB\).
What is a point in mathematics?
Theorem: The midline of a triangle is parallel to one of its sides and equal to half of that side. C. Altitude of a right triangle drawn from the vertex right angle, divides a triangle into two similar ones right triangle, each of which is similar this triangle. C. An inscribed angle subtended by a semicircle is a right angle. Here are the basic definitions, theorems, and properties of figures on the plane.
The vector with the coordinates of the point is called a normal vector; it is perpendicular to the line.
In a systematic presentation of geometry, a straight line is usually taken as one of the initial concepts, which is only indirectly determined by the axioms of geometry.
4. Two divergent lines on a plane either intersect at a single point, or they are parallel. A ray is a part of a straight line limited on one side. A segment, like a straight line, is denoted by either one letter or two. IN the latter case these letters indicate the ends of the segment.
Straight line - one of fundamental concepts geometry.
Clearly straight line can demonstrate a taut cord, the edge of a table, the edge of a sheet of paper, a place, the junction of two walls of a room, a beam of light. When drawing straight lines, a ruler is used in practice.
Straight line have such characteristic peculiarities:
1.U straight line there is no beginning or end, that is, it is endless . It is possible to draw only part of it.
2.In two arbitrary points can be carried out straight line, and only one at that.
3. Through n arbitrary point can be carried out not limited quantity straight lines in the plane.
4.Two mismatched straight lines on a plane or intersect at a single point, or they parallel.
To indicate straight line use either one small letter Latin alphabet, or two capital letters, written in two different places on this line.
If you indicate on a straight line point, then as a result we get two beam:
Beam call part straight line, limited on one side. To designate a beam, either one small letter of the Latin alphabet or two large letters are used, one of which is designated at the beginning of the beam.
The part of a straight line limited on both sides is called segment. A segment, like straight line, is designated either by one letter or two. In the latter case, these letters indicate the ends of the segment.
A line formed by several segments that do not lie on the same straight line is usually called broken line. When the ends of the broken line coincide, then broken line is called closed.
Point O splits line AB into two parts. What does each part resemble? How does each part differ from a straight line and a segment?
Mark the beginning of each ray with a colored pencil. How is the first ray designated? Is it possible to swap letters? Why? Label the remaining rays.
Solution
Using a ruler, trace the straight lines in the drawing with a red pencil, the rays with blue, and the segments with green:
- closed if its beginning and end are at the same point,
- open if its beginning and end are not connected
- self-intersecting
- without self-intersections
- intersecting if they have common point. Two lines can intersect only at one point.
- perpendicular if they intersect at right angles (90°).
- Parallel, if they do not intersect, do not have a common point.
- located on the same straight line
- start at one point
- directed in one direction
- ✂ B A ✂
A segment is denoted by two capital (capital) Latin letters, where the first is the point at which the segment begins, and the second is the point at which the segment ends
segment AB
A broken line is a line consisting of consecutively connected segments not at an angle of 180°
A long segment was “broken” into several short ones
- Through two points you can draw a single straight line.
- Two lines can intersect only at one point.
- Through one point you can draw infinite set straight
- Lowercase Latin letter:
- Lowercase Latin letter:
closed lines
open lines
self-intersecting lines
lines without self-intersections
straight lines
broken lines
curved lines
A straight line is a line that is not curved, has neither beginning nor end, it can be continued endlessly in both directions
Even when a small section of a straight line is visible, it is assumed that it continues indefinitely in both directions
Indicated by a lowercase (small) Latin letter. Or two capital (capital) Latin letters - points lying on a straight line
straight line a
Direct may be
parallel lines
intersecting lines
perpendicular lines
A ray is a part of a straight line that has a beginning but no end; it can be continued indefinitely in only one direction
The ray of light in the picture has its starting point as the sun.
A point divides a straight line into two parts - two rays A A
The beam is designated by a lowercase (small) Latin letter. Or two capital (capital) Latin letters, where the first is the point from which the ray begins, and the second is the point lying on the ray
The rays coincide if
rays AB and AC coincide
rays CB and CA coincide
A segment is a part of a line that is limited by two points, that is, it has both a beginning and an end, which means its length can be measured. The length of a segment is the distance between its starting and ending points
Through one point you can draw any number of lines, including straight lines
Through two points - an unlimited number of curves, but only one straight line
curved lines passing through two points
straight line AB
A piece was “cut off” from the straight line and a segment remained. From the example above you can see that its length is the shortest distance between two points.
The links of a broken line (similar to the links of a chain) are the segments that make up the broken line. Adjacent links are links in which the end of one link is the beginning of another. Adjacent links should not lie on the same straight line.
The vertices of a broken line (similar to the tops of mountains) are the point from which the broken line begins, the points at which the segments that form the broken line are connected, and the point at which the broken line ends.
A broken line is designated by listing all its vertices.
broken line ABCDE
vertex of polyline A, vertex of polyline B, vertex of polyline C, vertex of polyline D, vertex of polyline E
broken link AB, broken link BC, broken link CD, broken link DE
link AB and link BC are adjacent
link BC and link CD are adjacent
link CD and link DE are adjacent
The length of a broken line is the sum of the lengths of its links: ABCDE = AB + BC + CD + DE = 64 + 62 + 127 + 52 = 305
A polygon is a closed polyline
The sides of the polygon (it will help you remember the expressions: “go in all four directions”, “run towards the house”, “which side of the table will you sit on?”) are the links of a broken line. Adjacent sides of a polygon are adjacent links of a broken line.
The vertices of a polygon are the vertices of a broken line. Adjacent vertices are the endpoints of one side of the polygon.
A polygon is denoted by listing all its vertices.
closed polyline without self-intersection, ABCDEF
polygon ABCDEF
polygon vertex A, polygon vertex B, polygon vertex C, polygon vertex D, polygon vertex E, polygon vertex F
vertex A and vertex B are adjacent
vertex B and vertex C are adjacent
vertex C and vertex D are adjacent
vertex D and vertex E are adjacent
vertex E and vertex F are adjacent
vertex F and vertex A are adjacent
polygon side AB, polygon side BC, polygon side CD, polygon side DE, polygon side EF
side AB and side BC are adjacent
side BC and side CD are adjacent
CD side and DE side are adjacent
side DE and side EF are adjacent
side EF and side FA are adjacent
A B C D E F 120 60 58 122 98 141
The perimeter of a polygon is the length of the broken line: P = AB + BC + CD + DE + EF + FA = 120 + 60 + 58 + 122 + 98 + 141 = 599
A polygon with three vertices is called a triangle, with four - a quadrangle, with five - a pentagon, etc.
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Basics of geometry
Geometry is a branch of mathematics that studies geometric figures and their properties.
Let's get acquainted with the main geometric concepts, studied in elementary school.
A point is the basic and simplest geometric figure.
In geometry, a point is designated by a capital Latin letter or number. Many Latin letters are written similar to English letters.
In the text, a point is denoted by the following symbol: “(·) A” - point “A”.
A straight line is the simplest geometric figure that has neither beginning nor end.
The words “has neither beginning nor end” indicate that the line is infinite.
Ways to designate straight lines
Two capital Latin letters if these letters indicate points located on a straight line. 
A ray is a part of a straight line that is located on one side of a point. The ray has a beginning, but no end.
Ways to designate rays
Two capital Latin letters in the case when the first point is the beginning of the ray, and the second point lies on the ray. 
A segment is a part of a straight line that is bounded by two points (ends of the segment). A segment has both a beginning and an end.
The main property of a segment is its length.
The length of a segment is the distance between its ends.
In mathematics, a segment is denoted by capital letters.
A polyline is a geometric figure consisting of points that are connected by segments.
The vertices of a polyline are the points at which the segments that form the polyline are connected.
The links of a polyline are segments of a polyline.
In mathematics, a broken line is denoted in capital Latin letters.
Broken ABCD.
The vertices of the broken line are A, B, C, D.
The links of the polyline are AB, BC, CD.
To find the length of a broken line, you need to add up the lengths of all its links (segments) of which it consists.
KLCM = KL + LC + CM = 3 cm + 2 cm + 2 cm = 7 cm
This is how we met basics of geometry. Now we are ready to consider the equally important geometric figure- corner. To do this, go to the next page by clicking on the “View topic content” button at the top of the page.
Dot. Segment. Beam. Straight. Number line
We will look at each of the topics, and at the end there will be tests on the topics.
Point in mathematics
What is a point in mathematics? Mathematical point has no dimensions and is designated in capital Latin letters: A, B, C, D, F, etc.
In the figure you can see an image of points A, B, C, D, F, E, M, T, S.
Segment in mathematics
What is a segment in mathematics? In mathematics lessons you can hear the following explanation: a mathematical segment has a length and ends. A segment in mathematics is the set of all points lying on a straight line between the ends of the segment. The ends of the segment are two boundary points.
In the figure we see the following: segments ,,,, and , as well as two points B and S.
Direct in mathematics
What is a straight line in mathematics? The definition of a straight line in mathematics is that a straight line has no ends and can continue in both directions indefinitely. A line in mathematics is denoted by any two points on a line. To explain the concept of a line to a student, you can say that a line is a segment that does not have two ends.
The figure shows two straight lines: CD and EF.
Beam in mathematics
What is a ray? Definition of a ray in mathematics: a ray is a part of a line that has a beginning and no end. The name of the beam contains two letters, for example, DC. Moreover, the first letter always indicates the starting point of the beam, so letters cannot be swapped.
The figure shows the rays: DC, KC, EF, MT, MS. Beams KC and KD are one beam, because they have a common origin.
Number line in mathematics
Definition of a number line in mathematics: a line whose points mark numbers is called a number line.
The figure shows the number line, as well as the OD and ED rays
Basic geometric shapes
TO basic geometric shapes on the plane relate dot And straight line. Segment, beam, broken line- the simplest geometric figures on a plane.
The point is the smallest geometric figure, which is the basis of all other constructions (figures) in any image or drawing.
Any more complex geometric figure is a set points who have a certain property, characteristic only for this figure.
A straight line, or straight line, can be thought of as an infinite number of points, which are located on one line that has neither beginning nor end. On a piece of paper we see only part of a straight line, since it is infinite. The straight line is depicted like this:
Part straight line, bounded on both sides dots, is called a line segment, or line segment. The segment is depicted like this:
A beam is a directed half-line that has point beginning and has no end. The beam is depicted like this:
If on direct you put point, then this point splits the straight line into two beam, oppositely directed. Such rays are called additional.
broken line- that's a few segments, interconnected so that the end of the first segment is the beginning of the second segment, and the end of the second segment is the beginning of the third segment, etc., while adjacent (having one common point) the segments are not located on the same straight line. If the end of the last segment does not coincide with the beginning of the first, then such a broken line is called open.
Above is a three-link broken line.
If the end of the last segment of a broken line coincides with the beginning of the first segment, then such a broken line is called closed. An example of a closed polyline is any polygon:
Four-link closed polyline - quadrilateral
Three-link closed polyline - triangle
A plane, like a straight line, is a primary concept that has no definition. A plane, like a straight line, cannot see either the beginning or the end. We consider only the part of the plane that is limited by a closed polyline.
Example plane is the surface of your desktop, a notebook sheet, any smooth surface. The plane can be depicted as shaded
geometric figure:
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