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 .
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
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.
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.