The circle is a figure which is limited to a circle. Diameter of a circle is a chord which passes through its center. Diameter of this figure is designated by d or D. It is measured in meters, centimeters, millimeters.
It is required to you
- Calculator, ruler, roulette, meter.
Instruction
1. If in a mathematical task the area of a circle is known to you, and it is necessary to find its diameter, then use the following formula: s=pi*r^2 where s is the area of a circle (units of measure: square meters, square centimeters, square millimeters), r is the circle radius (the piece which connects the center of a circle to its border, is measured in meters, centimeters, millimeters), pi is a mathematical constant, in a decimal numeral system approximately equal 3.14.
2. From this formula express r (the following formula has to turn out: r= a root square of (s/pi)). Substitute in it the known sizes, find r and calculate diameter of a circle, having increased its radius by two (d=2*r).
3. By analogy solve the following problem. Task: Find diameter of a circle if its area (s=12.56 of centimeters) is known. Check whether correctly you solved it. Answer: d=8 of centimeters.
4. For example, before you a task in which circle length is known and it is necessary to find its diameter, then use the following formula: c=2*pi*r, where with - circle length (units of measure: meters, centimeters, millimeters). From this formula express r (the following formula will turn out: r=c / (2*pi). Substitute in it what is already given, find r and calculate diameter of a circle, having increased its radius by two (d=2*r).
5. Solve the following problem. Task: Find diameter of a circle if its length is known (from =12.56 centimeters). Check correctness of the decision. Answer: centimeter d=4.
6. If you need to measure diameter of a circle not theoretically, and practically, then use a ruler, a roulette or meter. The ruler is a simplest measuring tool which is a plate with the put divisions. The roulette is the film which is curtailed in a circle with divisions for measurements, the meter is a ruler with divisions into centimeters for measurement.