We start with a given circle.

Geometry construction with compass and straightedge or ruler or ruler
1.  Place the right-angle corner of any object at any point on the circle. Any point will do. Geometry construction with compass and straightedge or ruler or ruler
2.  Make a mark where the two sides of the right-angle cross the circle. Geometry construction with compass and straightedge or ruler or ruler
3.  Draw a line between these two marks. Because of Thales Theorem, this is a diameter of the circle. Geometry construction with compass and straightedge or ruler or ruler
4.  Place the right-angle corner of the object at any other point on the circle. Any point will do, but for greatest accuracy, make it about a quarter the way round the circle from the first point. Geometry construction with compass and straightedge or ruler or ruler
5.  Make a mark where the two sides of the right-angle cross the circle. Geometry construction with compass and straightedge or ruler or ruler
6.  Connect these two points with a straight line. This is the second diameter. Geometry construction with compass and straightedge or ruler or ruler
7.  Done. The point where the two diameters intersect is the center of the circle. Geometry construction with compass and straightedge or ruler or ruler

Why it works

Geometry construction with compass and straightedge or ruler or rulerThis method works as a result of Thales Theorem. The diameter of a circle subtends a right angle to any point on the circle. The converse is also true: A right angle on the circle must cut off a diameter. By finding two diameters, we find the center where they intersect

Visit Thales Theorem for an animated description of how this works.

Views: 255

Replies to This Discussion

This just solved a problem I was anticipating I would run into later. Now I know how to avoid it.

RSS

The Essential Pages

New to Cigar Box Nation? How to Play Cigar Box GuitarsFree Plans & How to Build Cigar Box GuitarsCigar Box Guitar Building BasicsCigar Box Guitar Parts Store

Site Sponsor

Recommended Links & Resources

Discussion Forum

Piezo feedback problems

Started by David Fultz. Last reply by Bernie Edwards Aug 27, 2016. 14 Replies

Bowed instruments

Started by Fomhorach. Last reply by JL Mar 23, 2016. 1 Reply

Ceramic piezo disc as a mic for a reverb spring

Started by Jon Leslie/Runaway Veal Music. Last reply by Fomhorach Mar 1, 2016. 6 Replies

Distortion

Started by Kevin M. Kraft. Last reply by Fomhorach Feb 29, 2016. 16 Replies

Stomp box

Started by smojo. Last reply by JL Jan 4, 2016. 14 Replies

DIY Tremolo

Started by Better Trees. Last reply by Better Trees Mar 10, 2014. 4 Replies

wiring mystery

Started by bucky. Last reply by Bernie Mango Feb 28, 2014. 5 Replies

Fever dream pickup

Started by Bear Peterson Jan 23, 2014. 0 Replies

Ted's Headstock Designs

Started by Ted Crocker. Last reply by Ted Crocker Sep 1, 2013. 2 Replies

Fretting Tips, Tricks & Supplies

Started by Ted Crocker. Last reply by Silent Jim Dec 21, 2011. 1 Reply

How to Find the Center of a Dowel or Circle

Started by Ted Crocker. Last reply by Ryan Rose Nov 6, 2011. 1 Reply

Nut & Bridge Slotting

Started by Ted Crocker. Last reply by Mark Werner Oct 18, 2011. 1 Reply

Printable Harbor Freight Tools Discount Coupons

Started by Ted Crocker. Last reply by Bear Oct 17, 2011. 1 Reply

Ted's Wiring Diagrams & Schematics

Started by Ted Crocker Oct 17, 2011. 0 Replies

Identifying Exotic Woods

Started by Ted Crocker Oct 17, 2011. 0 Replies

not cbg sorry

Started by jon beel. Last reply by ian dawson Sep 28, 2011. 3 Replies

circuit sniffing

Started by petey twofinger. Last reply by Chuck Dubman Jan 5, 2011. 3 Replies

2 prong outlet guitar chord?

Started by Jerryrig240. Last reply by Chuck Dubman Jan 2, 2011. 6 Replies

beer bottle caps

Started by smojo. Last reply by Nick Jan 4, 2010. 8 Replies

Blog Posts

New Member need a little advice.

Posted by Don Paul on January 26, 2020 at 10:29am 5 Comments

Neck bowing

Posted by Mike Kinzie on January 24, 2020 at 5:38pm 2 Comments

Dual lap steel

Posted by Ron Lutz on January 9, 2020 at 2:42pm 4 Comments

My 3 Gitty Kits

Posted by Poorness Studios on January 8, 2020 at 9:20am 2 Comments

My CBG details

Posted by Paul scofield on January 1, 2020 at 9:22am 2 Comments

Latest Activity

Bob Johnston commented on Poorness Studios's video
Thumbnail

Doesn't Remind Me

"Nice cover Kale.  Enjoyed this split screen product."
25 minutes ago
Bob Johnston commented on Bob Johnston's photo
Thumbnail

20191231_111209 (1)

"Thanks Jerry.  I have two more Ashtons,  one larger and the other one smaller than…"
32 minutes ago
Mineiro´s Blues posted a video

You Gotta Movie - The Little Jam Session Cigar Box Guitar

You Gotta Movie - The Little Jam Session Cigar Box Guitar. Uma pequena Jam com o meu novo projeto Cigar Box Guitars @Mineirosblues - Facebook/Instagram
35 minutes ago
Preston J. Laisure posted an event
Thumbnail

February Meeting of CBG Minded Michigan'ders at Red Sky Stage

February 8, 2020 from 1pm to 5pm
Monthly meeting to plan events, help each other with building questions, suggestions, etc. Some…See More
37 minutes ago
Danny Boy Davidson commented on BUGGY (C)'s video
Thumbnail

When life goes wrong, as it ain't just for free...

"Thats crazy stats on crashes. i be like " nope im good". ..im ok with coward right now."
47 minutes ago
Danny Boy Davidson liked BUGGY (C)'s video
47 minutes ago
Danny Boy Davidson commented on Andries D. EKER's video
Thumbnail

Garry Winogrand American Photographer A D Eker 2020

"i never heard of him?but i like looking up history stuff/ events. Thanks A.D."
52 minutes ago
Danny Boy Davidson liked Andries D. EKER's video
52 minutes ago
Taffy Evans replied to Brent Kasl's discussion Correcting a back bowed neck
"Hi If I can just make an comment here......a truss rod or reinforcing bar is usually used to…"
1 hour ago
Shane Speal shanespeal.com posted a video

The Electro-Diddley: Sound Test, Fret Markers, Star Spangled Banner

The Electro-Diddley, as featured in Poor Man's Guide Magazine https://poormansguitar.com/poor-man-s-guide-magazine Shane Speal takes the one-string electric ...
2 hours ago
3 String Guitars posted a video

Acoustic Cigar Box Resonator - Recording of a 3 string guitar

recording of a resonator cigar box guitar from the website https://www.reddogguitars.com/ There is also lots of old time blues music recorded on cigar box gu...
2 hours ago
BUGGY (C) posted a video

When life goes wrong, as it ain't just for free...

....there is still love. 4 Sting CBG
2 hours ago

Music

Loading…

© 2020   Created by Ben "C. B. Gitty" Baker.   Powered by

Badges  |  Report an Issue  |  Terms of Service

\uastyle>\ud/** Scrollup **/\ud.scrollup {\ud background: url("https://storage.ning.com/topology/rest/1.0/file/get/963882636?profile=original") no-repeat scroll 0 0 transparent;\ud bottom: 25px;\ud display: inline !important;\ud height: 40px;\ud opacity: 0.3 !important;\ud position: fixed;\ud right: 30px;\ud text-indent: -9999px;\ud width: 40px;\ud z-index: 999;\ud}\ud.scrollup:hover {\ud opacity:0.99!important;\ud}\ud \uascript type="text/javascript">\ud x$(document).ready(function(){\ud x$(window).scroll(function(){\ud if (x$(this).scrollTop() > 100) {\ud x$('.scrollup').fadeIn();\ud } else {\ud x$('.scrollup').fadeOut();\ud }\ud });\ud x$('.scrollup').click(function(){\ud x$("html, body").animate({ scrollTop: 0 }, 600);\ud return false;\ud });\ud });\ud \ua!-- End Scroll Up -->