You will need

- - the radius of the circle:
- - the length of the arc of the chord;
- - angle of the arc of the chord;
- paper and drawing tools.

Instruction

1

Follow the drawing in accordance with the conditions of the problem. Draw a circle of a given radius. If you know the angle of the arc which subtends a chord, build it. Swipe radius, put a protractor to the desired angle and do another. The point of intersection of the radii with the circumference of connect direct. This will be the desired chord. If the angle is unknown, draw a random

**chord**.2

Follow these additional construction. Divide

**the chord**in half and flick to this point, the perpendicular from the centre of the circle. You get an isosceles triangle, the altitude of which is perpendicular to the middle of the chord.3

Label the radius as R,

**the chord**- like h, and the Central angle A. Then h is fashionable to calculate using either the sine or cosine through. In the first case the formula will look like h=2R*sinA/2, where R is the known radius of the circle. In the second case the formula will look like h=R*√(1-cosB).4

One of the most ancient geometric problems - to find the length of chord if you know the radius of a circle and arc length. Calculate the length of the circle P. It is equal to twice the radius multiplied by the factor P it can be expressed by the formula P=2PR.

5

Calculate the ratio of a given arc length l to the circumference P. This way you calculate the size of the arc angle. In this case, it can be in degrees or radians. Knowing the size, compute the sine of half-angle. Then you can calculate the size of the chord on the already known formula.

6

Often faced with the opposite task - for example, find the arc length and the radius of the circle and the chord length. Using theorem of sines, calculate the size of the half, and then an entire Central angle. Knowing him, the ratio of arc length to the circumference, calculate the unknown length of the arc.

Useful advice

With the longest chord is the diameter, usually act differently. Of course, it is possible for these ratios to calculate it, but the angle is known in advance and is 180°. In this case, sinA/2=sin90°=1. Accordingly, h=2R*sinA/2=2R.

When calculating the size of any direct way or another connected with the circumference, it is advisable to finish the drawing so as to obtain triangles whose parameters are known. In the case of chord you have used several properties of the line. For example, the fact that the perpendicular drawn to the chord from the center of the circle divides the chord in half.

When calculating the size of any direct way or another connected with the circumference, it is advisable to finish the drawing so as to obtain triangles whose parameters are known. In the case of chord you have used several properties of the line. For example, the fact that the perpendicular drawn to the chord from the center of the circle divides the chord in half.

# Advice 2: How to calculate percentage

One-hundredth of a whole is called the percentage. If this integer value is composed of several separate parts, each of them can be measured in hundredths of the whole.

**The ratio**of the magnitudes of these components will be called a percentage. Practical calculation it is not difficult and consists of several simple mathematical operations.Instruction

1

Find out what the values should be based on the expectation value of one percent. For example, if a drug consists of two ingredients, three-dimensional characteristics are known, then the whole should be the sum of these two known values and calculate the value of one percent, dividing that amount into one hundred parts. For example, if ready to eat the paint contains eight hundred milliliters of the actual paint and four hundred milliliters of solvent, then the one percent will be expressed the value of twelve ounces, as (800+400)/100=12.

2

Find the percentage expression of each of compared values, dividing the value of each of the components of the integer values calculated in the previous step size one percent. For example, the amount of dye in solution from the example in the previous step will be about 67 percent, as 800/12=66,6666667. And the volume of solvent of the same example is equal to approximately 33 percent, so 400/12=33,3333333. These two numbers will Express the percentage of the components of ready solution components.

3

Use for calculations, for example, built into the Windows operating system software calculator, if you calculate values in mind is not possible. To access this application through a standard dialog box run programs by calling it by pressing shortcut keys win + r.

4

In dialogue it is necessary to type the command calc and click on the "OK" button. The calculator interface is extremely simple, and the sequence of several operations of division and multiplication, as described in the previous steps, is unlikely to cause any difficulties.

# Advice 3: How to calculate the chord of a circle

According to the definition of a curve in analytic geometry it represents a set of points. If any pair of such points to connect the cut, it can be called a chord. Outside of higher education institutions often consider the chord pertaining to the curve of the correct form, and in most cases this curve is a circle. To compute the length of chord connecting two points

**of a circle**, not very difficult.Instruction

1

If you draw two radii to the points

**of a circle**, the bounding**chord**, and the angle between them will be called "Central". At a certain value of this angle (θ) and the radius**of the circle**(R) length of the chord (d) determine, after considering the isosceles triangle formed by these three lines. Since the known angle is opposite the desired side (the base of the triangle), the formula must contain twice the product of the radius by the sine of half that angle: d = 2*R*sin(θ/2).2

Two points lying on a

**circle**together with a chord specify the boundary of some arc on the curve. Arc length (L) uniquely determines the value of the Central angle, so if it is given in terms of the problem along with the radius**of the circle**(R), to calculate the length of the chord (d) is also possible. The measure of the angle in radians expresses the ratio of arc length to radius L/R and in degrees, this formula should look like this: 180*L/(π*R). Substitute it into the equality of the previous step: d = 2*R*sin((180*L/(π*R))/2) = 2*R*sin(90*L/(π*R)).3

The size of the Central angle can be determined without the radius, if other than arc length (L) is known the total length

**of the circumference**(Lₒ) - it will be equal to the product of 360° to the length of the arc divided by the length**of a circle**: 360*L/Lₒ. And the radius can be expressed via the length**of the circumference**and the number PI: Lₒ/(2*π). Substitute all this into the formula from the first step: d = 2*Lₒ/(2*π)*sin((360*L/Lₒ)/2) = Lₒ/π*sin(180*L/ Lₒ).4

Knowledge of the square sector (S) carved in a circle two radii (R), held at the extreme point of the chord will also allow us to calculate the length of this chord (d). The size of the Central angle in this case can be defined as the ratio between twice the square and the squared radius: 2*S/R2. Substitute this expression in the same formula from the first step: d = 2*R*sin((2*S/R2)/2) = 2*R*sin(S/R2).

# Advice 4: What about a chord in the heart

False chords are most often found in the hearts of men. This is a small abnormal formation of the ventricles, usually the left. Chord is not considered a pathology, but requires medical supervision and compliance with certain limitations.

Instruction

1

The notochord is an extra formation of connective tissue. The tumor is attached to the wall of the partition located between the ventricles, or directly to the walls of the ventricle. This files most often about the chord formed in the left ventricle and are most of the adult population. Usually located in the middle of education, but they are apical, and basal. In the direction of the chord distinguish between transverse, diagonal and longitudinal.

2

Chords can be single or multiple. To detect the presence of false chords listening is impossible, since they do not affect the tone of the heart. Usually find them at the cardiology examination and diagnosed according to the testimony of echocardiography. In good physical condition of the person about chords do not cause discomfort and painful sensations. However, examination of the heart it is necessary to inform about their presence, as the chord "noise" and, therefore, can prevent to hear abnormal noises.

3

If you increase physical exertion and the presence of many false chords quickens the heart rhythm that can cause a visit to the doctor. In case you have more chords people must be under the supervision of a cardiologist and to undergo regular check on the ECHO control.

4

People diagnosed with false chords are exempt from military service, they also contraindicated in professional sport, they put themselves at risk while scuba diving, or skydiving. A person who has a false chord in the heart, must lead a healthy lifestyle, to avoid heavy physical exertion.

5

Among newborn babies quite often diagnose the presence of false chords. The treatment itself is not, however, for a child up to 6 months, establish patronage, and a year and a half, it observes a cardiologist, in the absence of other abnormalities, the child is considered healthy. Control tests are held in years 3 and 7 years before kindergarten and school, in order to determine group health.

6

To panic due to the presence of chords in a child's heart need not, over the years, this body is growing, and the chord shifted so that they are aware, it is almost impossible to diagnose.

7

It is believed that the reason for the formation of chords – heredity, passed on from mother to child. The first sign of the presence of the chord is the low endurance of a relatively healthy person, a way of dealing one moderate exercise and a balanced diet.