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: 251

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

Latest Activity

Jack Brady liked cbgkent's video
38 minutes ago
KOOL DOG HOOCH posted a discussion
39 minutes ago
Dave Lynas commented on Dave Lynas's photo
Thumbnail

Sunday Morning Duke

"Yup BQ. Getting his wiring done is taking more attention than planned. :*/"
2 hours ago
Tyler Jones joined Shane Speal shanespeal.com's group
Thumbnail

Building a Cigar Box Guitar 101

This group is for discussing the basics of CBG building for newer builders - where to start, what…See More
3 hours ago
Tyler Jones liked Shane Speal shanespeal.com's group Building a Cigar Box Guitar 101
3 hours ago
Tyler Jones left a comment for rotten roger
"You make great guitars and great teacher for folks thanks Tyler "
3 hours ago
Glenn Kaiser commented on Glenn Kaiser's photo
Thumbnail

MontecristoDiddley

"Thanks Brian Q, fun build, sounds great. -Glenn"
3 hours ago
cbgkent commented on cbgkent's video
Thumbnail

How to remove unwanted stickers easily

"Thanks guys, put a hairdryer on the Xmas wishlist!!"
4 hours ago
the anonymous pick posted a photo

WITCH CERTIFICATES

GREAT GIFT IDEA.NO LATE GIFTS , (GIVE THEM THE CERTIFICATE ON XMAS) - THEN LET ME PLAN THEIR GUITAR…
5 hours ago
Dennis "Denbo" Goodinson liked Poorness Studios's video
5 hours ago
Dennis "Denbo" Goodinson commented on Uncle John's video
Thumbnail

Pawn Shop Christmas Commercial

"Sorry UJ I won't need any washing it's taken care of free. Neither will I ever need any…"
5 hours ago
Dennis "Denbo" Goodinson liked Uncle John's video
5 hours ago

Music

Loading…

© 2019   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 -->