My Math Forum Constant angle protractor?

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 June 7th, 2018, 01:02 AM #1 Newbie   Joined: Jun 2018 From: Norway Posts: 2 Thanks: 0 Constant angle protractor? Is there a protractor/compass that keeps a constant angle where one arm automatically moves the other arm? Say the protractor is closed at a 0 degree angle, you move one arm and the arm follows exactly opposite to it on the other side? Protractor.jpg
 June 7th, 2018, 01:35 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,918 Thanks: 2201 I doubt it.
 June 7th, 2018, 02:00 AM #3 Newbie   Joined: Jun 2018 From: Norway Posts: 2 Thanks: 0 Mmm, there must be something like this, if not a geometry tool
 June 7th, 2018, 03:49 AM #4 Global Moderator   Joined: Dec 2006 Posts: 20,918 Thanks: 2201 Various adjustable linkages exist, so perhaps there's one that would do what you want if set up correctly.
 June 7th, 2018, 06:42 AM #5 Senior Member   Joined: Apr 2014 From: UK Posts: 953 Thanks: 340 You want one of these: https://image.dhgate.com/0x0/f2/albu...PYXpbhA857.jpg
 June 7th, 2018, 06:49 AM #6 Senior Member   Joined: Apr 2014 From: UK Posts: 953 Thanks: 340 If you attach a piece of cork to the end and point a laser distance measuring device at it, you can read off the angle Thanks from jonah
June 7th, 2018, 06:58 AM   #7
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Quote:
 Originally Posted by stoob Is there a protractor/compass that keeps a constant angle where one arm automatically moves the other arm? Say the protractor is closed at a 0 degree angle, you move one arm and the arm follows exactly opposite to it on the other side? Attachment 9755
Yes, of course, carpenters use them and I believe Stanley tools make one.
The simplest ones are just two arms like you show with a large locking wingnut at the pivot so you can set the angle.

Equally my adjustable draughtsman's square has this ability.

 June 7th, 2018, 09:46 AM #8 Global Moderator   Joined: Dec 2006 Posts: 20,918 Thanks: 2201 What causes the arms to move in opposite directions?
 June 7th, 2018, 11:31 AM #9 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond Build one and patent it, then see how well it does.

 Tags angle, constant, protractor

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