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Finding the center of a circle or arc
Geometry construction using a compass and straightedge
This page shows how to find the center of a circle or arc with compass and straightedge or ruler.
This method relies on the fact that, for any
chord
of a circle, the
perpendicular bisector
of the chord always passes through the center of the circle. By applying this twice to two different chords, the center is established where the two bisectors intersect. A Euclidean construction
Printable step-by-step instructions
The above animation is available as a
printable step-by-step instruction sheet, which can be used for making handouts
or when a computer is not available.
Try it yourself
Click here for a printable worksheet containing two center-finding problems.
When you get to the page, use the browser print command to print as many as you wish. The printed output is not copyright.
Constructions pages on this site
Lines
Angles
Triangles
Triangle Centers
Circles, Arcs and Ellipses
Polygons
Non-Euclidean constructions
(C) 2009 Copyright Math Open Reference. All rights reserved
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