As a rule, in tasks in geometry, as well as in practical affairs, diameter of a circle is set and it is required to find its length. But there are situations when the return is necessary — length of a circle is known and it is necessary to calculate its other parameters. At a lesson of mathematics or drawing there can be a need to learn circle radius before to draw it. In practical life there are situations too. For example, you know the size of a hat and want to construct its pattern.
It is required to you
- Compasses
- Concept of radius, diameter and length of a circle
- Circle length formula
Instruction
1. Remember what is length of a circle and as it is measured. In practical life flexible measuring devices, like a centimetric tape or a roulette for this purpose are usually used. If you need to learn diameter of the basis of a cylinder, it is possible to make at first its development, having circled the basis and having constructed a side surface. Basis circle length in this case will be equal to basis length.
2. Remember on what formula circle length is calculated. Designate circle length as With, its radius — as R, diameter — as D. Length of a circle is equal to the doubled work of radius on number?, C=2? R. Remember what is diameter of a circle. It is also the doubled radius.
3. Find the doubled circle radius. 2R=C/?. Thus, D=C/?. Remember what the number is equal to?. It is equal to 3, 14. Divide circle length into this number. For determination of radius it is necessary received private to divide into 2. Draw a circle on the received radius.
4. Having learned radius length, it is possible to determine also the area of a circle. It needs to be made if, having made a pattern of a round hat, you want to calculate. How many material is required. Designate the area of a circle as S. It will be equal to number?, increased by a radius square.