If you work with a circle, you often use terms the radius and diameter. There is a number of the simple formulas allowing to find radius, knowing the circle length, the area of a circle and volume of the sphere. Whether there is a formula allowing to learn radius, knowing value of diameter?
Instruction
1. Diameter (from Ancient Greek διάμετρος "diameter, diameter") is a piece which connects two points on a circle or the sphere, passing through the center of this circle or the sphere. Diameter is also called length of this piece. Radius (from Latin radius "beam, wheel needle") is a piece which connects the center of a circle or the sphere to any point which is on this circle or the sphere, radius is called also length of this piece.
2. Radius can be designated by letter r, diameter – letter d. By definition the radius is equal to a half of diameter, and diameter is equal in size to two radiuses. According to d=2r, r=d/2. Means to learn radius size, knowing diameter, it is necessary to divide diameter into two.
3. Example. Diameter of a circle of d is equal to 8. What is r radius equal to? Decision: r=d/2, so to find radius, it is necessary 8 to divide value of diameter into two. 8/2=4. Answer: r=4, radius is equal to four.
4. If you look for length of radius or diameter, you remember that length cannot be a negative number. Therefore if during the decision you came to a formula d=2r = √x (a square root from x), and x is equal, for example 16, then diameter of d=±4, and r=±2 radius. As length cannot be a negative number, receive the answer: diameter is equal to four, radius is equal to two.
5. The fact that in anatomy the word "radius" also meets is interesting, it designates one of forearm bones, a beam bone (there are knaruzh and slightly kpered from an elbow bone). And still the word radius has a value going sources to ancient Rome is the name of a short Roman sword which was used by legionaries for defense. The legionary said: "Here I and Rome!" – drew on the earth this sword a strip and it was protected to the last.