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Good Geometry tools for constructions


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The most important tool for construction, IMO, is a really good compass. The plastic compasses at Walmart are complete carp. You want metal. The ability to lock the radius is a nice feature which helps for precise construction.

One of the best brands is Rotring (we bought ours in Europe; the brand may be less common in the US). This one looks similar:

 

http://www.amazon.com/Alvin-Premium-Silverline-Compass/dp/B001DKHL3U/ref=pd_sim_sbs_hg_6

Edited by regentrude
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We have liked the set from Right Start for Intermediate Geometry. It does not contain a traditional compass, but accomplishes the task with another instrument (can't remember name).

 

http://store.rightstartmath.com/rightstartand153geometryset.aspx

 

Good Luck!

 

So how do they use the tools in the picture to replace a compass for classical construction (i.e. problems like halving an angle, perpendicular bisector, etc)? very curious.

Edited by regentrude
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So how do they use the tools in the picture to replace a compass for classical construction (i.e. problems like halving an angle, perpendicular bisector, etc)? very curious.

 

That blue tool in the middle is used for the compass. Their geometry is really a great program. RightStart begins using the tools in their first grade program, so I believe they use the substitute for safety reasons. The complete kit is used for their middle school geometry, and I think they should have added a traditional compass to that kit.

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That blue tool in the middle is used for the compass. Their geometry is really a great program.... The complete kit is used for their middle school geometry, and I think they should have added a traditional compass to that kit.

 

:iagree: I think learning to use a traditional compass is valuable and we did add one in for certain tasks. My biggest thought on this program is just how good it is and how overlooked it seems to be. It would be very rigorous for a 5th grader (5th-8th is rec) and was tough for my ds who was in 7th. We only completed 1/2 of it because a tree fell through our house that Nov and we spent 4 months in a hotel learning a lot of life skills while rebuilding.

 

I had chosen it as a "filler" for ds who I didn't think was quite ready for algebra at the time. It was billed as Intermediate Math and good for strengthening basic skills. In addition to being a good refresher, I thought he would enjoy applying that knowledge through all the hands-on constructing that is often absent from traditional proof-based courses in HS. Interestingly, many of its fun applications are similar to those found in the Developmental Geometry course I see recommended here. It's all in b/w, so not quite as appealing, but the work is solid. Also, it introduces 2-column proofs from a mathematical properties perspective and this was a bit hard for ds. However, he was able to tell me his thought process and I then converted it the format so he could see it.

 

He will probably do Holt Geometry 2007 for 10th grade, but regardless of the final choice, I am going to have him complete the last 1/2 of the RS Geometry course.

 

Honestly, for a non-mathy HS student, I would probably consider it for a geometry credit. I couldn't find a sample TOC online, but it is fairly comprehensive.

 

JMHO!

 

ETA: That should read Discovering Geometry!

Edited by PameLA in VA
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The most important tool for construction, IMO, is a really good compass. The plastic compasses at Walmart are complete carp. You want metal. The ability to lock the radius is a nice feature which helps for precise construction.

One of the best brands is Rotring (we bought ours in Europe; the brand may be less common in the US). This one looks similar:

 

http://www.amazon.com/Alvin-Premium-Silverline-Compass/dp/B001DKHL3U/ref=pd_sim_sbs_hg_6

 

This is exactly what I need; a compass that locks the radius. We had such frustration with other compasses that would not lock into place. Just wish it wasn't so pricey but as my dh always says, "You get what you pay for".

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This set gets good reviews - from a geometry teacher too.

 

http://www.amazon.com/Maped-Geometry-Assortment-Shatterproof-897010/dp/B003155XYO/ref=dp_cp_ob_op_title_2

 

I'm not familiar with Right Start' date=' but I would definitely not skip doing constructions with a traditional compass. IMO this is a basic geometry skill.[/quote']

 

This looks nice as well and the price is definitely right. I am just concerned about the compass reviews.

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We have liked the set from Right Start for Intermediate Geometry. It does not contain a traditional compass, but accomplishes the task with another instrument (can't remember name).

 

http://store.rightstartmath.com/rightstartand153geometryset.aspx

 

Good Luck!

Thanks for the recommendation. I think we want to go with a more traditional compass.

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This looks nice as well and the price is definitely right. I am just concerned about the compass reviews.

 

There is one reviewer who claims the compass is terrible, but that doesn't seem to be the general consensus. We bought a different one which I wouldn't recommend. :tongue_smilie:

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what you want is a Bow Compass. It will have a thumbwheel which will allow you to lock in the radius. I prefer the compasses with the thumbwheel in the center rather than on the side. You should be able to pick up a good one for about $10 at OfficeMax, OfficeDepot, Staples, Hobby Lobby, or Michael's.

 

I also highly recommend a mechanical pencil over a wooden pencil. Accuracy in geometric constructions is crucial.

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This came up at epsilon camp when i had to order compasses for the 28 kids ages 8-10. I tried a lot of different ones and bought several including an expensive thumb wheel one (staedtler) that locks firmly in place.

 

The only drawback I found to the "good" one is that although it does stay where you want it, it does not change easily to another setting. You have to slowly screw the thumbwheel out a microscopic amount at a time. that takes forever to go from a small setting to a large one.

 

i found it so tedious to use for more than one radius setting that I stopped using it and never used it again. Maybe Kareni has some tips to share on this.

 

The plastic ones were useless to me because they slipped while I was trying to draw a circle, although my 10 year old granddaughter could manage it oddly enough. i eventually found lots of simple metal ones for one or two dollars. I bought about 40 of the one dollar ones and that worked fine. They were metal but so cheap they did break occasionally, but I had extras. But just one won't suffice, so

 

I would suggest maybe the two dollar ones as more substantial. But I myself would only use the super precise twelve dollar ones or more, if someone is very patient. Oh and the precise one also has a rather sharp point, I stuck myself painfully.

 

I would use the most basic metal one, like I had in high school, but sturdy. Here is a picture of it, but this ridiculous price is about 6 or 8 times too high.

 

http://www.schoodoodle.com/home/sch/page_1679/metal_ball_bearing_compass_12_pack_with_safety_poi.html?rid=thefind&utm_source=thefind&utm_medium=feed&utm_campaign=thefind

 

Maybe Kathy in Virginia remembers where we got those. I spent a long time searching for a decent price.

 

As a disclaimer, I did not achieve terrific accuracy with my basic compasses every time. It was somewhat hit or miss. So maybe those here who advocate staedtler are right, if you want really good results.

 

Here are some of those. Mine looked like the 6'' student one. I got it at an art supply store for about $12.

 

http://www.google.com/#q=staedtler+compass&hl=en&tbm=shop&prmd=imvns&ei=KJr4T6qSJ4ec8gTVgd2VCQ&start=10&sa=N&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=ecd0620c0a53f36f&biw=1268&bih=653

 

 

which one is being recommended? My staedtler says "Mars 551, and Comfort".

Edited by mathwonk
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… I would use the most basic metal one, like I had in high school, but sturdy. Here is a picture of it, but this ridiculous price is about 6 or 8 times too high.

 

http://www.schoodoodle.com/home/sch/page_1679/metal_ball_bearing_compass_12_pack_with_safety_poi.html?rid=thefind&utm_source=thefind&utm_medium=feed&utm_campaign=thefind …

 

The link is for $15.15 for a 12 pack - probably not so ridiculous!

 

mathwonk, btw, I am loving your posts.

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The only drawback I found to the "good" one is that although it does stay where you want it, it does not change easily to another setting. You have to slowly screw the thumbwheel out a microscopic amount at a time. that takes forever to go from a small setting to a large one.

 

 

Sometimes, you can speed up the change by applying very light force to the two arms, just below the threaded rod, squeezing inward. This takes the pressure off the setup, and you can often spin the thumbwheel more quickly.

 

HTH

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