A circle is a closed curved line, each point of which is located at the same distance from one point O, called the center.
Straight lines connecting any point of the circle with its center are called radii R.
A line AB connecting two points of a circle and passing through its center O is called diameter D.
The parts of the circles are called arcs.
A line CD joining two points on a circle is called chord.
A line MN that has only one point in common with a circle is called tangent.
The part of a circle bounded by a chord CD and an arc is called segment.
The part of a circle bounded by two radii and an arc is called sector.
Two mutually perpendicular horizontal and vertical lines intersecting at the center of a circle are called circle axes.
The angle formed by two radii of KOA is called central corner.
Two mutually perpendicular radius make an angle of 90 0 and limit 1/4 of the circle.
Division of a circle into parts
We draw a circle with horizontal and vertical axes that divide it into 4 equal parts. Drawn with a compass or square at 45 0, two mutually perpendicular lines divide the circle into 8 equal parts.
Division of a circle into 3 and 6 equal parts (multiples of 3 by three)
To divide the circle into 3, 6 and a multiple of them, we draw a circle of a given radius and the corresponding axes. The division can be started from the point of intersection of the horizontal or vertical axis with the circle. The specified radius of the circle is successively postponed 6 times. Then the obtained points on the circle are successively connected by straight lines and form a regular inscribed hexagon. Connecting points through one gives an equilateral triangle, and dividing the circle into three equal parts.
The construction of a regular pentagon is performed as follows. We draw two mutually perpendicular axes of the circle equal to the diameter of the circle. Divide the right half of the horizontal diameter in half using the arc R1. From the obtained point "a" in the middle of this segment with radius R2, we draw an arc of a circle until it intersects with the horizontal diameter at point "b". Radius R3 from point "1" draw an arc of a circle to the intersection with a given circle (point 5) and get the side of a regular pentagon. The "b-O" distance gives the side of a regular decagon.
Dividing a circle into N-th number of identical parts (building a regular polygon with N sides)
It is performed as follows. We draw horizontal and vertical mutually perpendicular axes of the circle. From the top point "1" of the circle we draw a straight line at an arbitrary angle to the vertical axis. On it we set aside equal segments of arbitrary length, the number of which is equal to the number of parts into which we divide the given circle, for example 9. We connect the end of the last segment with the lower point of the vertical diameter. We draw lines parallel to the obtained one from the ends of the segments set aside to the intersection with the vertical diameter, thus dividing the vertical diameter of the given circle into a given number of parts. With a radius equal to the diameter of the circle, from the lower point of the vertical axis we draw an arc MN until it intersects with the continuation of the horizontal axis of the circle. From points M and N we draw rays through even (or odd) division points of the vertical diameter until they intersect with the circle. The resulting segments of the circle will be the desired ones, because points 1, 2, …. 9 divide the circle into 9 (N) equal parts.
To find the center of an arc of a circle, you need to perform the following constructions: on this arc, mark four arbitrary points A, B, C, D and connect them in pairs with chords AB and CD. We divide each of the chords in half with the help of a compass, thus obtaining a perpendicular passing through the middle of the corresponding chord. The mutual intersection of these perpendiculars gives the center of the given arc and the circle corresponding to it.
Instruction
smash circle into four equal parts is very simple, it is a trivial task. To do this, you just need to draw two center lines perpendicular to each other. The points at the intersection of these lines with circle yu and her into four parts. More common to divide circle not four, but eight equal parts. In order to do this, you will need to divide the arc, which is one quarter of the circle, into two equal parts. Then take the compass and spread it to the distance indicated in the image by color. Now it remains just to postpone this distance from each of the four points obtained earlier.
In order to break circle into three equal parts, spread the legs to the radius of the circle. After that, install the compass needle at any point of intersection of the axial lines and the circle. Draw a thin line to help circle. Three equal parts by intersection points and auxiliary circles, as well as a point that lies on the line, or rather at its opposite end.
And if you need to share circle into six equal parts, then you need to do almost everything the same. The only difference is that these must be repeated for the other centerline. In this case, you get six points on the circle at once, as shown in the figure.
It is often necessary to separate circle into five equal parts. This is also not difficult to do. First you need to divide the radius on the centerline into two equal parts. It is at this point that the needle of the compass is needed. The stylus must be retracted to the point of intersection of the circle and the center line perpendicular to this. You can clearly see this in the figure. On it, this distance is shown in red. Lay this distance on the circle. You need to start from the center line, and then transfer the needle to the new resulting intersection point. To break circle for ten parts, repeat all the above steps in a mirror.
Division of a circle into three equal parts. Install a square with angles of 30 and 60 ° with a large leg parallel to one of the center lines. Along the hypotenuse from a point 1 (first division) draw a chord (Fig. 2.11, a), getting the second division - point 2. Turning the square and drawing the second chord, get the third division - point 3 (Fig. 2.11, b). By connecting points 2 and 3; 3 and 1 straight lines form an equilateral triangle.
Rice. 2.11.
a, b - c using a square; in- using a circle
The same problem can be solved using a compass. By placing the support leg of the compass at the lower or upper end of the diameter (Fig. 2.11, in) describe an arc whose radius is equal to the radius of the circle. Get the first and second divisions. The third division is at the opposite end of the diameter.
Dividing a circle into six equal parts
The compass opening is set equal to the radius R circles. From the ends of one of the diameters of the circle (from the points 1, 4 ) describe arcs (Fig. 2.12, a, b). points 1, 2, 3, 4, 5, 6 divide the circle into six equal parts. By connecting them with straight lines, they get a regular hexagon (Fig. 2.12, b).
Rice. 2.12.
The same task can be performed using a ruler and a square with angles of 30 and 60 ° (Fig. 2.13). The hypotenuse of the square must pass through the center of the circle.
Rice. 2.13.
Dividing a circle into eight equal parts
points 1, 3, 5, 7 lie at the intersection of the center lines with the circle (Fig. 2.14). Four more points are found using a square with angles of 45 °. When receiving points 2, 4, 6, 8 the hypotenuse of a square passes through the center of the circle.
Rice. 2.14.
Dividing a circle into any number of equal parts
To divide a circle into any number of equal parts, use the coefficients given in Table. 2.1.
Length l chord, which is laid on a given circle, is determined by the formula l = dk, where l- chord length; d is the diameter of the given circle; k- coefficient determined from Table. 1.2.
Table 2.1
Coefficients for dividing circles
To divide a circle of a given diameter of 90 mm, for example, into 14 parts, proceed as follows.
In the first column of Table. 2.1 find the number of divisions P, those. 14. From the second column write out the coefficient k, corresponding to the number of divisions P. In this case, it is equal to 0.22252. The diameter of a given circle is multiplied by a factor and the length of the chord is obtained l=dk= 90 0.22252 = 0.22 mm. The resulting length of the chord is set aside with a measuring compass 14 times on a given circle.
Finding the center of the arc and determining the size of the radius
An arc of a circle is given, the center and radius of which are unknown.
To determine them, you need to draw two non-parallel chords (Fig. 2.15, a) and set up perpendiculars to the midpoints of the chords (Fig. 2.15, b). Centre O arc is at the intersection of these perpendiculars.
Rice. 2.15.
Pairings
When performing machine-building drawings, as well as when marking workpieces in production, it is often necessary to smoothly connect straight lines with arcs of circles or an arc of a circle with arcs of other circles, i.e. perform pairing.
Pairing called a smooth transition of a straight line into an arc of a circle or one arc into another.
To build mates, you need to know the value of the radius of the mates, find the centers from which the arcs are drawn, i.e. interface centers(Fig. 2.16). Then you need to find the points at which one line passes into another, i.e. connection points. When constructing a drawing, mating lines must be brought exactly to these points. The point of conjugation of the arc of a circle and a straight line lies on a perpendicular lowered from the center of the arc to the mating line (Fig. 2.17, a), or on a line connecting the centers of mating arcs (Fig. 2.17, b). Therefore, to construct any conjugation by an arc of a given radius, you need to find interface center and point (points) conjugation.
Rice. 2.16.
Rice. 2.17.
The conjugation of two intersecting lines by an arc of a given radius. Given straight lines intersecting at right, acute and obtuse angles (Fig. 2.18, a). It is necessary to construct conjugations of these lines by an arc of a given radius R.
Rice. 2.18.
For all three cases, the following construction can be applied.
1. Find a point O- the center of the mate, which must lie at a distance R from the sides of the corner, i.e. at the point of intersection of lines passing parallel to the sides of the angle at a distance R from them (Fig. 2.18, b).
To draw straight lines parallel to the sides of an angle, from arbitrary points taken on straight lines, with a compass solution equal to R, make serifs and draw tangents to them (Fig. 2.18, b).
- 2. Find the junction points (Fig. 2.18, c). For this, from the point O drop perpendiculars to given lines.
- 3. From point O, as from the center, describe an arc of a given radius R between junction points (Fig. 2.18, c).
During repairs, you often have to deal with circles, especially if you want to create interesting and original decor elements. It is also often necessary to divide them into equal parts. There are several methods to do this. For example, you can draw a regular polygon or use tools known to everyone since school. So, in order to divide the circle into equal parts, you will need the circle itself with a well-defined center, a pencil, a protractor, as well as a ruler and a compass.
Dividing a circle with a protractor
Dividing a circle into equal parts using the above tool is perhaps the easiest. We know that a circle is 360 degrees. By dividing this value by the required number of parts, you can find out how much each part will take (see photo).
Further, starting from any point, you can make notes corresponding to the calculations. This method is good when the circle needs to be divided by 5, 7, 9, etc. parts. For example, if the figure needs to be divided into 9 parts, the marks will be at 0, 40, 80, 120, 160, 200, 240, 280 and 320 degrees.
Division into 3 and 6 parts
To correctly divide the circle into 6 parts, you can use the property of a regular hexagon, i.e. its longest diagonal must be twice the length of its side. To begin with, the compass must be stretched to a length equal to the radius of the figure. Then, leaving one of the legs of the tool at any point on the circle, the second one needs to be marked, after which, repeating the manipulations, it will turn out to make six points, by connecting which you can get a hexagon (see photo).
By connecting the vertices of the figure through one, you can get a regular triangle, and accordingly the figure can be divided into 3 equal parts, and by connecting all the vertices and drawing diagonals through them, you can divide the figure into 6 parts.
Division into 4 and 8 parts
If the circle needs to be divided into 4 equal parts, first of all, it is necessary to draw the diameter of the figure. This will allow you to get two of the required four points at once. Next, you need to take a compass, stretch its legs along the diameter, after which one of them should be left at one of the ends of the diameter, and the other should be made notches outside the circle from the bottom and top (see photo).
The same must be done for the other end of the diameter. After that, the points obtained outside the circle are connected with a ruler and a pencil. The resulting line will be the second diameter, which will be clearly perpendicular to the first, as a result of which the figure will be divided into 4 parts. In order to obtain, for example, 8 equal parts, the resulting right angles can be divided in half and diagonals drawn through them.
Today in the post I post several pictures of ships and diagrams for them for embroidery with isothread (pictures are clickable).
Initially, the second sailboat was made on carnations. And since the carnation has a certain thickness, it turns out that two threads depart from each. Plus, layering one sail on the second. As a result, a certain effect of splitting the image appears in the eyes. If you embroider the ship on cardboard, I think it will look more attractive.
The second and third boats are somewhat easier to embroider than the first. Each of the sails has a central point (on the underside of the sail) from which rays extend to points along the perimeter of the sail.
Joke:
- Do you have threads?
- There is.
- And the harsh ones?
- It's just a nightmare! I'm afraid to come!
My first debut Master Class. Hopefully not the last. We will embroider a peacock. Product diagram.When marking the places of punctures, pay special attention so that they are in closed contours even number.The basis of the picture is dense cardboard(I took brown with a density of 300 g / m2, you can try it on black, then the colors will look even brighter), better dyed on both sides(for the people of Kiev - I took it in the stationery department at the Central Department Store on Khreshchatyk). Threads- floss (of any manufacturer, I had DMC), in one thread, i.e. we unwind the bundles into individual fibers. Embroidery consists of three layers thread. At first we embroider the first layer in feathers on the peacock's head, the wing (light blue thread color), as well as dark blue circles of the tail using the flooring method. The first layer of the body is embroidered with chords with variable pitch, trying to make the threads run tangentially to the contour of the wing. Then we embroider twigs (seam-snake, mustard-colored threads), leaves (first dark green, then the rest ...
