What is actually pie. The radius is a line that goes from the center to the rime of the circle in a straight line and the diameter is a line that goes from side to side of the circle, passing through the center in a straight line. Pie r ( radius ) squared is the formular for the area of the circle and when you need the circumfrance of the circle ( The perimeter ) then you use the formular Pie d ( which is pie times the diameter).
