How to calculate the diameter of a circle

As a rule, in problems of geometry, as well as in practical Affairs, is set to the diameter of a circle and want to find its length. But there are times when you need the opposite — the known length of the circumference and we must calculate the remaining parameters. In math class or sketching, you may need to know the radius of the circle, before it is drawn. In practical life also there are times. For example, you know the size of the hat and want to build her pattern.

You will need

• The compass
• The concept of radius, diameter and circumference
• The formula for the circumference of a circle

Instruction

1. Remember what the length of the circumference and how is it measured. In practical life this is usually used flexible measuring devices like a tape or tape measure. If you need to know the diameter of the cylinder base, you can make it scan, circling the base and building side surface. The length of the circumference of the base in this case will be equal to the length of the base.
2. Remember, what is the formula to calculate the length of the circumference. Indicate the length of a circle With radius as R, the diameter — as D. the Length of a circle is equal to twice the product of the radius by the number ?, C=2?R. Remember what the diameter of the circle. This is twice the radius.
3. Find twice the radius of the circle. 2R=C/?. Thus, D=C/?. Remember, what is the number ?. It is equal to 3, 14. Divide the length of the circumference by this number. To determine the necessary radius of the resulting quotient divided by 2. Will watertite a circle according to the obtained radius.
4. Knowing the length of the radius, one can determine the area of a circle. You must do this if making a pattern round the hat, you want to calculate. How much material is needed. Indicate the area of the circle as S. It will be equal to the number ?, multiplied by the square of the radius.