2. C=π d C=2πr r=½d d=rx2 A=πr²

3. The diameter is the longest chord. The ratio of the circumference is always 3.1415926…. π is a Greek letter. π can also be written as C 3.14d

4. minor arc- measures less than 180. major arc- measures more than 180. semicircle- measures exactly 180. example: (find C) diameter is 9-use formula C=πd C= π x 9 C=9 π Answer: C= about 28.3

5. circle- a set of points in a plane that are the same distance from a given point in a plane center- a given point in a plane radius- the segment from the center to any point on the circle diameter- a chord that passes through the center circumference- the distance around the circle π(pi)- 3.14 and circumference÷diameter