You will need

- - the length of the diameter of the circle.

Instruction

1

A circle is a figure in the plane consisting of a plurality of points disposed in the same distance from another point called the centre. A circle is a flat geometric figure, represents the set of points enclosed in a circle which is the boundary of the circle. Diameter is a segment that connects two points on the circle and passing through its center. The radius is the segment connecting a point on the circle and its center. π — the number "PI", a mathematical constant that is the constant. It shows the ratio of the circumference to the length of its

**diameter**. To compute the exact value of π is impossible. In geometry use the approximate value of this number: π ≈ 3,142

The area of a circle equals the product of the square of the radius to the number calculated by the formula: S=NR^2, where S is

**the area**of the circle, R is the length of the radius of the circle.3

From the definition of the radius, it follows that it is equal to half

**the diameter**. Hence, the formula becomes: S=π(D/2)^2, where D is the length**of the diameter**of the circle. Substitute in the formula the value**of the diameter**, calculate**the area**of a circle.4

The area of a circle is measured in square units — mm2, cm2, m2, etc. In what units is expressed you received

**the area**of a circle depends on what units was the diameter of a circle.5

If you need to calculate

**the area**of a ring use this formula: S=π(R-R)^2, where R, r are radii of the outer and inner circumferences of the ring, respectively.Useful advice

There is an international day of "PI", which is celebrated on March 14. The exact time of onset of the official date — 1 hour 59 minutes 26 seconds, according to figures the number is 3,1415926...