The number "пи" is the relation of length of a circle to its diameter. From here follows that length of a circle equals "p de" (C = π*D). Proceeding from this ratio it is simple to remove a formula of inverse relation, i.e. D=C/π.
It is required to you
- - calculator.
Instruction
1. To learn diameter of a circle, knowing its length, divide circle length into number "пи" (π), equal about three whole and fourteen 100-th (3.14). The value of diameter at the same time will turn out in the same units of measure, as circle length. This formula can be written down in the following look: D=C/π, where: With – circle length, π – number "пи", approximately equal 3.14.
2. PrimerDlina of the equator of Earth approximately equals 40,000 kilometers. To what does diameter of Earth equal? Decision: 40000/3.14=12739 (km). Answer: diameter of the earth equals about 12740 kilometers.
3. For more exact calculation of diameter of a circle use more exact representation of number "пи", for example: 3.1415926535897932384626433832795. Of course at all it is optional to use all signs of this number, for the majority of engineering calculations it is quite enough of 3.1416.
4. At calculation of diameter of a circle on the basis of its length, pay attention that on many (especially, engineering) calculators there is a special key for input of number "пи". Such button by an inscription on (over, under) it "π" or something similar is designated. So, for example, in the virtual Windows calculator the corresponding button is designated as pi. Use of a special key allows to accelerate considerably input of number "пи" and to avoid mistakes at its input. Besides, the number "пи", stored in memory of the calculator, is presented with an accuracy, greatest possible for each device, there.
5. Sometimes measurement of length of a circle is the only almost acceptable way to learn its diameter. Especially it concerns pipes and cylindrical designs, "not having the beginning and the end".
6. To measure the circle length (cross section) of a cylindrical subject, take a thread or a rope of sufficient length and wind it around this cylinder (in one turn).
7. If very high precision of measurements is necessary or the subject has very small diameter, then wrap up a cylinder several times, and then divide length of a thread (rope) into quantity of turns. In proportion to quantity of rounds also the accuracy of measurement of length of a circle, and, respectively, and calculation of its diameter will increase.