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# Posts

### April 26, 2015

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Un chemin pour comprendre comment un traité scientifique de grande valeur, écrit au IIe av. J.-C., peut encore être lu aujourd'hui. - Histoire des Mathématiques / Piste bleue, featured
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If is a noncommutative ring, then Morita theory tells us that cannot in general be recovered from its category of modules; that is, there can be a ring , not isomorphic to , such that . This means, for example, that “free” is not a categorical property of modules, since it depends on a choice […]
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Twitter once provided RSS feeds for all Twitter accounts. They no longer provide this service. However, third parties can create RSS feeds from the content of Twitter accounts. BazQux has done this for my daily tip accounts, so you can subscribe to any of my accounts via RSS. AlgebraFact AnalysisFact CompSciFact Diff_eq MedVocab NetworkFact PerlRegex ProbFact […]

### April 25, 2015

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Ever found yourself describing a student or a class to another colleague as "low ability"? It's a shortcut we use more frequently than we may realise, even if said in the most caring, well-intentioned way. Early in my teacher education at Sydney University, I was very fortunate to be given a very simple and powerful idea: change one word.  Replace the word "ability" with "achievement". The result may surprise you. Here's my favorite example: next time you hear yourself saying: "Let's […]
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Many poems are written of baseball; a few of them involve mathematics --  see the posting for April 9, 2010 for math-related baseball poems by Marianne Moore (1877-1972) and Jerry Wemple; see the posting for September 18, 2011 for one by Jonathan Holden.     Today I feature the opening stanza from a baseball poem by Pennsylvania poet, Le Hinton. from   Our Ballpark    by Le Hinton       This is the place where my father […]
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Mathematics is like childhood diseases. The younger you get it, the better.~Arnold SommerfeldThe 116th day of the year; 116! + 1 is prime! *Prime Curios (Students might investigate how often n!+1 is prime)And:116^2 + 1 is primeThe number 1 appears 116 times in the first 1000 digits of pi. Thanks to *Math Year-Round ‏@MathYearRoundEVENTS1514 Nicolaus Copernicus (1473-1543) made his first observation of Saturn. Copernicus later proposed that the sun is stationary and that the Earth and the […]
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Thanks so much to everyone for trying out my transfinite epistemic logic puzzle, which I have now given the name Cheryl’s Rational Gifts, on account of her gifts to Albert and Bernard. I received many solution proposals, including numerous correct solutions … Continue reading →
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This year I’ve been using the Canvas learning management system primarily as a work flow tool–because that’s what it is–primarily. It’s heavy on teacher productivity. Post, turn in, provide feedback, and electronically grade assignments. Create pages for resources or a week-at-a-glance. Build modules to deliver content. But what are the students doing? For me the best feature […]
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Another book I bought somewhat on a whim, although I cannot remember which one… The latest edition has a preface by John Scalzi, author of Old Man’s War and its sequels, where he acknowledged he would not have written this series, had he previously read The Forever War. Which strikes me as ironical as I […]
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via PrettyMaths
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If we hung out at NCTM you might have noticed something different about my name tag. Not the amazing #MTBoS label, or my orange T (where are you bead buddy??) but the lanyard. I'm all about the recycling so I grabbed a comfy lanyard with an organization I don't mind advertising for. Teach plus is about creating opportunities for teacher leadership - those are leaders who are still in the classroom. This year I had the opportunity to join the teacher cabinet in Salem (where I live and work). I […]
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the “rotation model” suggested by the lower-left (addition-mod-3) table really only “works” for addition (insofar as it lacks any [obvious] *multiplicative identity*); so too for the “eight-hour shift” version (what would it *mean* to “multiply” by “adding 8 hours on a 12-hour clock”?). and working in color presents quite a few technical difficulties. so quite […]
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Time seems to be flying by now days. Pretty soon I’ll be back in the states to visit in June! I can’t wait. So, I think I left off at Easter. This was my first Easter in Peru, and let … Continue reading →
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On Friday afternoon Anna (@borschtwithanna) tweeted out this call for conversation:Hey #MTBoS, teach me how to go over hw. I give answer keys, but it still takes like half the period to answer questions & make connections— Anna Blinstein (@Borschtwithanna) April 24, 2015What followed was a virtual master class on handling homework in different settings. It's the sort of conversation that the #MTBoS excels at, pulling in thoughtful responses from teachers at every level of practice.I've […]
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Images by Thea Schultheiss   http://im-possible.info/english/art/pencil/thea-schultheiss.html   Author - https://windigoheart.wordpress.com/
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My students took their end-of-instruction exam on April 13th.  That was two weeks ago, and we still have three weeks left in the school year.  My students and I worked extremely hard to cover the entire curriculum before Spring Break began.  Now that testing is over, it's been a full-time job keeping them busy.  I know a lot of people are probably reading this right now and thinking that I should still be teaching new content.  That just isn't feasible with how my […]
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A Geometric Proof of Proizvolov's Identity
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From Arbitrary Hexagon to Regular One
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Given three squares BCDE, ABIF, and ACJG, the latter two with centers O and O'. Let P be the midpoint of DG, N that of EF, S the intersection of NO' and OP. Then AS passes through M, the midpoint of DE
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As teachers, we don’t typically like to admit when we don’t know something in front of our peers and especially in front of our students. Luckily for us, if we can stall long enough to get to our phone, Google has made it quite handy in making those moments extremely short-lived. The unique opportunity of […]
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Number lines are a fantastic tool!  Make sure your students have their own laminated ones.  Also, make sure that you have them on your walls and your floors.  Yes, even in the upper grades.  Make sure you have fraction and decimal number lines up! Link  (scroll towards the bottom to see number lines) Happy Mathing, […]
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als wenn ein Hubschrauber auf dem Sportplatz landet, um einen Schüler ins Krankenhaus zu fliegen. Wer immer es war, ich wünsche dem oder derjenigen, dass alles gut gehen wird.
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^ >==========> ^ | . . . . . . .| |…………..| |…………..| |…………..| ^ >==========> ^ the interior of our square can be conveniently co-ordinatized as I = { (x,y) | 0 < x < 1, 0 < y < 1}. the *boundary*, ƍ(I), then consists of four line segments L = {(0,y) | […]
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<!--[if gte mso 9]> <![endif]--> ΑΝΑΜΗΣΕΙΣ ΣΥΜΜΕΤΡΙΑΣ Μια μυθιστορηματική περιήγηση στο έργο του χαράκτη Μάουριτς Κορνέλις Έσερ του Ανδρέα Λύκου, Εκδόσεις Γαβριηλίδη, 2015 Βιβλιο-παρουσίαση από τον Θωμά Βουγιουκλή Το βιβλίο είναι μια καλαίσθητη έκδοση, 160 σελίδων με […]
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My friend David Miller is looking for instructors to help out with the Newton Girls who Code club.  Here's an announcement, please connect with him if you're interested.  They visited Harvard last week -- David gave me permission to post his description of the visit.  It seemed like a well-organized event -- thanks to the Harvard Women in Computer Science group for putting it together.---- Last Friday, the Newton Girls Who Code club was welcomed by the Harvard […]
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T. M. Scanlon is one of the foremost moral and political philosophers alive. But he started as a logician, working with Benacerraf as an undergraduate at Princeton, Dummett during a Fulbright at Oxford, and Dreben for his Ph.D. at Harvard. His first two papers were: The Consistency of Number Theory Via Herbrand’s Theorem, JSL 38…
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updated definition
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I saw two neat problems for kids on twitter this week and went through them with the boys this morning. First up, the problem shared by David Coffey: I couldn’t find any multicolored items to use, so we used snap cubes instead of cards. The first thing that we tried to do is see if…
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A while ago I shared some thoughts about my iPad workflow (singular). Maybe you read it? A non-descript tall man did and then it got retweeted to the moon and back.I didn't touch on the logistics much. It is not a 1:1 environment. The classes that used these the most had 36, 35, and 34 kids in them. Sharing was required.Here are the ingredients of the tasks:iPad/iPhone sitting on the same wireless network as my teaching computerDesmosPagesBrother HL-3170CDWhandyPrint (\$5), makes USB connected […]