Instruction
1
A circle is a closed curve. The points that lie in its plane, equidistant from the centre, which lies in one plane together with a curve. Radius - a segment of a circleconnecting its center with any point. With its help, you can learn many other parameters of the figure, so it is a key parameter. The numerical value of the radius will be the length of this segment.
2
You should also distinguish the radius of the shape from its diameter (diameter connects the two most remote from each other point). To use a mathematical method of finding the radius you need to know the length or diameter of the circle. In the first case the formula will look like R = L/2?", where L is the known length of the circumference, and the number ? equal to 3.14 and is used to denote a particular irrational number.
3
In the case that the only known diameter, the formula will look like R = D/2".
4
If the length of the circle is unknown, but there are data on the length and height of a segment, the formula would be R = (h^2*4 + L^2)/8*h where h is the height of the segment is the distance from mid-chord to the most protruding part of the said arc) and L is the length of the segment (which is not the chord length).Chord – a line segment that connects two points of a circle.
Note
It is necessary to distinguish the concept of "circumference" and "circle". The circle is part of the plane, which, in turn, is limited by the circumference of a certain radius. To find the radius, you must know the area of a circle. In this case, the equation would be R = (S/π)^1/2, where S is a square. To calculate the area, in turn, should know the radius (S = NR^2").
