This line is perfect - says us mind when we see before ourselves a circle. Really, thanks to its property - its all points are equidistanted from the center - it seems such proportional and graceful. But this harmony conceals in itself ""reef"" - how to calculate its length?
Instruction
1. As is well-known from school textbooks, a circle - a locus of the plane, equidistanted from the set point called by the center on the set nonzero distance called its radius. Measurement of its length, in comparison with measurement of length of a piece of a straight line or perimeter of geometrical figures, is more difficult operations because the circle does not consist, owing to definition, of a set of pieces of a straight line, and is a curve which each point is equally removed from the center of a circle.
2. Two sizes - the radius (the straight line piece connecting the center of a circle and a point on a circle) and a mathematical constant are necessary for finding of length of a circle? (p), understood as circle length with a diameter equal to unit (diameter - the straight line piece which is connecting two points of a circle (chord) and passing through its center). Measurement of radius if it is in advance unknown, can be made by means of a ruler: the maximum distance between two points of a circle is its diameter. Radius, in turn is a half of diameter. Number? - constant, approximately equal 3.1415926535.
3. Knowing the radius of a circle and number?, it is possible to calculate the circle length equal to the work of the specified constant and the radius increased by 2 (see a formula on fig. 1 where C - length of a circle, R - radius).