The center of a circle can be determined by finding the point of intersection of the perpendicular bisectors of two of its chords. This is accomplished using a compass and a ruler.
- Draw two chords
Draw two chords on the circle using a ruler. For greatest accuracy, avoid chords that are nearly parallel.
- Construct perpendicular bisectors on the chords.
Put the compass at one end of the chord. With a compass width that is about two-thirds of the chord, draw arcs above and below it. Without changing the compass width, repeat this on the other end of the chord. Using a ruler, join the two points where the arcs intersect. Repeat this on the other chord.
- Find the point of intersection of the bisectors
The point of intersection of the two lines created above is the center of the circle.