- Q.If I am presented with a
portion of a circle (an arc), how can I determine the size
(diameter) of the circle that the arc is part of?
responds: First, connect any two points of the arc with a
straight line. Find the center of that line and draw a
perpendicular line through the center point. Then do the same
thing again elsewhere on the arc — connect two points
with a straight line and draw a perpendicular line through the
center of that line.
The point where the two perpendicular lines cross is the
center of the circle.
Finding the Center of a