Circle Geometry & Pi

Circumference: The perimeter of a circle.

Diameter: A line that goes from one side to another PASSING THROUGH THE MIDDLE.

Radius: A line that goes from one part of the circumference (ark) to the middle point.

Chord: A line that goes from one part of a circle to anther part of the circle NOT PASSING THROUGH THE MIDDLE.

Ark: The segment or proportion of the circumference.

Sector: The area of two radii.

Segment:The area between the ark and a chord.

Tangent: A line that just meets at the surface of a circle once.

Pi is the ratio of the circumference to the diameter. That is, π=\frac{C}{D}

Pi can be used in many ways, for e.g. finding the circumference of a circle. These are the two formulas for finding the circumference and the area of a circle which uses Pi.

r = radius of a circle

1. circumference = 2πr or πD 
2. area = πr²

For example if a question asks you find the area of the circle if the radius = 5. You do:

1. A=πr²
2. A=3.14×5²
3. A=3.14×25
4. A=78.5

Another example is. Find the circumference of the circle if the radius = 3

1. C=2πr
2. C=2×3.14×3
3. C=18.84

Or

1. C=πD
2. C=3.15x3x2( you multiply it by 2 because the Diameter is double)
3. C=18.84

Now you know more about pi and the properties of a circle, congratulations!!!