You will need

- Protractor, ruler.

Instruction

1

Let the known length of the chord AB and the angle AOB between the

**radii**conducted to the ends of the chord. We find these data the radius of the circle with center at point O.2

Triangle AOB is isosceles because OA = OB = R. By a property of an isosceles triangle the height of the OE is a median and a bisector of the angle AOB. Denote the angle AOB for x

Triangle AEO is rectangular with right angle AEO. Since the height TH is also the bisector of the angle AOB, the angle AOE = x/2. Then from the right triangle AOE, we have: OA = R = (AB/2)/sin(x/2).

Triangle AEO is rectangular with right angle AEO. Since the height TH is also the bisector of the angle AOB, the angle AOE = x/2. Then from the right triangle AOE, we have: OA = R = (AB/2)/sin(x/2).

# Advice 2 : How to calculate the length of a circle

The circle represents a part of the plane bounded by a circle. Like the circle,

**the circle**has its center, length, radius, diameter, and and and other characteristics. In order to calculate**the length****of the circle**, you will need to do some simple actions.You will need

- Depending on the situation you might need to know either the radius or diameter of a circle.

Instruction

1

First and foremost is to understand what data will be manipulated in order to find

**the length****of the circle**. For example, given a circle whose radius is equal to R. the radius of the circle (**the circle**) is a segment that unites the center of the circle (**the circle**) with any of the points of the circle. If given a circle whose radius is unknown, then the problem will be referred to is not the radius but the diameter of this circle, which is conventionally equal to D. In this case, it is worth remembering that the radius length equal to half the length of the diameter. Diameter is a segment that connects any two opposite points together of the circumference, which restricts the plane, forming the circle, while the segment passes through the center of this**circle**.2

Having dealt with the source task data, you can use one of two formulas for finding the circumference of a circle/

C = π*D, where D is the diameter of this

C = 2*π*R, where R is the radius.

**circle**:C = π*D, where D is the diameter of this

**circle**;C = 2*π*R, where R is the radius.

3

You can consider the examples.

Example 1: Given a circle whose diameter is 20 cm, it is required to find its

C = 3.14*20 = 62.8 cm

Answer: the length of this

Example 2: Given a circle whose radius is 10 cm, is required to compute its

C = 2*3.14*10 = 62.8 cm

The answers are the same, because the radii of the circles given in the examples are equal.

Example 1: Given a circle whose diameter is 20 cm, it is required to find its

**length**. To solve this problem you will need to use one of the formulas mentioned above:C = 3.14*20 = 62.8 cm

Answer: the length of this

**circle**is 62.8 cmExample 2: Given a circle whose radius is 10 cm, is required to compute its

**length**. Assuming that the radius**of the circle**is known, you can use the second formula:C = 2*3.14*10 = 62.8 cm

The answers are the same, because the radii of the circles given in the examples are equal.

Note

PI is a constant value which is equal to 3.14. This constant is not rounded in that case, if you require high accuracy calculations. This is important in architecture, mechanics, physical computing, and many other areas. Then π = 3.1415926535