How to Define Characteristics of a Circle

A circle is a line that continues to curve without end. Every measured point along the boundary of a circle is equal from the circle's center. A circle has a diameter, radius, circumference, and arc. An important aspect of measure circles is to understand and know the value of PI . PI is a ratio with a value approximately 3.141592654... PI has an infinite, non-repeating decimal value.

Difficulty: Moderate

Instructions

1. 
    
   Diameter

   The diameter of a circle is the distance of a line that starts from one end of the circle and ends at the other end of the circle and traveling through the circle's center point. The value of PI is determined by dividing the value of the circle's circumference by the value of the circle's diameter.

2. 
    
   Radius

   A radius is half the distance of a diameter of a circle. A radius is formed by drawing a line starting from the center of a circle and ending at a circle's boundary. PI is equal to the length of the circumference of the circle divided by 2 times the radius of that circle.

3. 
    
   Circumference

   The circumference of a circle is the distance around it. Both the starting point and ending point are the same. The circumference is PI multiplied by the diameter of a circle (or by 2 times the length of the circle's radius).

4. 
    
   Arc

   An arc is a section of a circumference with a starting and ending point which are not the same.

Tips & Warnings

• The area of a circle is determined by multiplying the value of PI by the value of the circle's radius squared.
• The length of an arc is determined by value of its angle. For example, if the angle value from point A to point B along the circumference of a circle is 20 degrees. Divide 20 into 360 (20/360 = .056) and multiply the result by the value of the circumference. If the value of the circumference is 10 inches, they the length of the arc is .056 times 10 which results in .56 inches.