Instruction

1

If you divide the metric value of a circle's circumference to its diameter, it is always in private you will get the same number: 3,14.However, the fraction is infinite, but for any size of the circles is the same. It is a universal number called letters of the Greek alphabet "PI .

2

Now, in any practical case where you will need to know the diameter of some circle, for example: lids on the tank, the hatch, sotovoi the roof of the pit, round the ravine and so forth, you can measure the circumference of the ring, quickly calculate its diameter.It only necessary to apply the formula of circumference of a circle.L = p DЗдесь:L is the circumference,n is the number of PI = 3.14,D is the diameter of the circle.Rearrange the formula for the circumference of a circle required to the left side and get:D = L/p

3

Let us examine a practical problem. Suppose you need to make a cap for the country round the well, accessed in the moment. Not the season, and unsuitable weather conditions. But do you have data on

*the length*of its circumference. Let's assume it is 600, see specified formula substitute the values:D = 600/3,14 = 191.08 see now, 191 cm is the diameter of your well.Increase the diameter to 2 metres, given the extra thickness at the edges. Set the compass to a radius of 1 m (100 cm) and vycherchivaya circumference.Useful advice

The circumference of relatively large diameters in the home is convenient to draw a compass that can be quickly manufactured. This is done so. The rail hammered two nails at a distance from each other equal to the radius of the circle. One shallow hammer a nail into the workpiece. And another use, the rotating rail as a marker.

# Advice 2: How to find the diameter of a circle

The circle is called a geometric figure in the plane consisting of all points in this plane are equidistant from a given point. Given the point is called the center

**of the circle**, and the distance at which points**of a circle**are its center, radius**of the circle**. The region of the plane bounded by a circle called the circle.There are several methods of calculating the**diameter****of a circle**, the choice of the specific depends on the available original data.Instruction

1

In the simplest case, if you construct a circle of radius R, then its diameter will be equal to

D = 2 * R

If the radius

D = L/N where L is the length

The diameter

D = 2 * v(S/P), where S is the area of a circle, N is the number of P.

D = 2 * R

If the radius

**of the circle**is not known, but is known for its length, the diameter can be calculated according to the formula of length**of circumference**D = L/N where L is the length

**of the circumference**, N is the number of P.The diameter

**of the circle**can be calculated by knowing the area of a circle it limitedD = 2 * v(S/P), where S is the area of a circle, N is the number of P.

2

In special cases the radius

If the circle inscribed in a triangle, then its radius is given by

R = S/p where S is the area of a triangle, p = (a + b + c)/2 – properiter triangle.

**of the circle**can be found if it is described or inscribed in a triangle.If the circle inscribed in a triangle, then its radius is given by

R = S/p where S is the area of a triangle, p = (a + b + c)/2 – properiter triangle.

3

For the

R = (a * b * c)/4 * S, where S is the area of a triangle.

**circle**described about a triangle, the formula for the radius has the formR = (a * b * c)/4 * S, where S is the area of a triangle.

# Advice 3: As for the circumference to find the diameter

Determining the diameter of a circle can be useful not only for solving geometric problems, but to help in practice. For example, knowing the diameter of the neck of the banks, you will not go wrong in choosing the cover for her. The same is also true for larger circles.

Instruction

1

Suppose you want to buy a cover for the well, but the exact diameter is not known, but known components, only the circumference.

2

So, enter the names of the variables. Let d – diameter of the well, L is the circumference, n is the number PI, whose value is approximately equal to 3.14, R is the radius of the circle. The circumference (L) are known. Assume that it is equal to 628 cm.

3

Then to find the diameter (d) use the formula for the circumference of a circle: L=2PR, where R is the unknown variable, L=628 cm, and p=3,14. Now use the rule to find unknown multiplier: "to find an unknown multiplier, we need work divided by the known multiplier." Obtained: R=L/2P. The substitute values to the formula: R=628/2x3. 14. Obtained: R=628/6,28, R=100 cm.

4

After the radius of the circle was found (R=100 cm), use the following formula: the diameter of a circle (d) is equal to two radii of the circle (2R). Turns out: d=2R.

5

Now, to find the diameter, substitute into the formula d=2R values and calculate the result. Since the radius (R), is obtained: d=2x100, d=200 cm.