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 Girls’ Angle Bulletin, Volume 13, Number 1
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 Girls’ Angle Bulletin, Volume 12, Number 6
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 A Student’s Perspective on a Math Collaboration
 Girls’ Angle Bulletin, Volume 13, Number 3
 Happy New Year 2019!
 Girls’ Angle Bulletin, Volume 12, Number 2
 Girls’ Angle Bulletin, Volume 12, Number 1
 Head Mentoring at Girls’ Angle
 Girls’ Angle Bulletin, Volume 11, Number 6
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Girls’ Angle Bulletin, Volume 12, Number 2
The electronic version of the latest issue of the Girls’ Angle Bulletin is now available on our website.
We open with the second part of a multipart interview with mathematician Dr. Kristin Lauter, a professor at the University of Washington and a principal researcher at Microsoft Research. In this segment, Dr. Lauter gets into the nittygritty details of the DiffieHellman protocol for public key exchange and begins to explain what elliptic curves have to do with cryptography.
Next, Prof. Needell teases us with some tantalizing probability questions to underscore just how subtle and surprising probability can be.
Alana AxelrodFreed, Milena Harned, and Miriam Rittenberg show how they proved a nifty result pertaining to paper folding that they discovered last summer. They were exploring the socalled “stamp folding problem” which asks for the number of ways a row of n stamps can be folded up by folding along the creases between stamps. This is an unsolved problem. However, they restricted to counting a certain subset of the folds and were able to get an explicit answer.
Emily and Jasmine begin a new math adventure exploring the areas of regions obtained by drawing zigzags across the face of a rectangle. The cover shows an example of such a dissection. Will they find any interesting patterns? What patterns will they find?
Next, we have an article that aims to help those who are struggling to understand a fourth spatial dimension. The strategy presented is a pair of parallel dialogues that is based on work I did with eighth graders at the Buckingham, Browne, and Nichols Middle School that seemed to be fairly effective at helping them move into the fourth dimension.
Milena and Miriam return with the second part of our article on Umbrellas. Here we complete the proof of a characterization of the locus of points reachable in n unitlength step from the origin, such that each step has a nonnegative vertical component.
We close with a few Notes from the Club.
We hope you enjoy it!
Finally, a reminder: when you subscribe to the Girls’ Angle Bulletin, you’re not just getting a subscription to a magazine. You are also gaining access to the Girls’ Angle mentors. We urge all subscribers and members to write us with your math questions or anything else in the Bulletin or having to do with mathematics in general. We will respond. We want you to get active and do mathematics. Parts of the Bulletin are written to induce you to wonder and respond with more questions. Don’t let those questions fade away and become forgotten. Send them to us!
We continue to encourage people to subscribe to our print version, so we have removed some content from the electronic version. Subscriptions are a great way to support Girls’ Angle while getting something concrete back in return. We hope you subscribe!
Girls’ Angle Bulletin, Volume 12, Number 1
The electronic version of the latest issue of the Girls’ Angle Bulletin is now available on our website.
Through the years, Dr. Kristin Lauter and Microsoft Research have been major financial supporters of Girls’ Angle, especially, our Math Collaboration initiative. Dr. Lauter is a Principal Researcher at Microsoft Research specializing in number theory and cryptography. We are thrilled to embark on a multipart interview with Dr. Lauter in this issue. The interview was conducted in person by Ke Huang, a graduate student in the department of applied mathematics at the University of Washington. The interview was transcribed by New England Transcription Services with further assistance from Harvard math graduate student Peter Park.
In the previous issue, Prof. Needell showed how unintuitive highdimensional geometry can be. In this issue’s installment of Needell in the Haystack, she exploits this unusual geometry to explain how to solve a problem in compressed sensing. In particular, she uses the fact that a corner of a highdimensional hyperoctahedron has smaller and smaller highdimensional solid angle. If you read this article and have trouble seeing this fact about hyperoctahedra, have no fear, Anna investigates the question in Anna’s Math Journal
Next up is a geometric result that Milena Harned, Miriam Rittenberg, and I stumbled upon a little over a year ago. The question is: For a fixed positive integer n, what is the locus of points that you can reach in a plane in n steps, where a step is one unit long and must have nonnegative vertical displacement. In Umbrellas, Part 1, we explain what the locus is for all n and prove it for n = 1 and 2. In the sequel, we will provide a proof for all n.
Harvard undergraduate Michael Kleistra gives us a chance to learn all about cardinality in a step by step installment of Learn by Doing.
Emily and Jasmine wrap up their investigation into stacked circles, seeking an elusive container for a stack of circles whose radii form a harmonic progression.
Addie Summer does more math while waiting for a bus.
And we close with a few Notes from the Club.
We hope you enjoy it!
Finally, a reminder: when you subscribe to the Girls’ Angle Bulletin, you’re not just getting a subscription to a magazine. You are also gaining access to the Girls’ Angle mentors. We urge all subscribers and members to write us with your math questions or anything else in the Bulletin or having to do with mathematics in general. We will respond. We want you to get active and do mathematics. Parts of the Bulletin are written to induce you to wonder and respond with more questions. Don’t let those questions fade away and become forgotten. Send them to us!
We continue to encourage people to subscribe to our print version, so we have removed some content from the electronic version. Subscriptions are a great way to support Girls’ Angle while getting something concrete back in return. We hope you subscribe!
Posted in math, Math Education
Tagged cardinality, circles, compressed sensing, Deanna Needell, geometry, greatest common factor, harmonic progressions, hyperoctahedra, Ke Huang, Kristin Lauter, least common multiple, Michael Kleistra, Milena Harned, Miriam Rittenberg, Peter Park, umbrellas, unit vectors
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Head Mentoring at Girls’ Angle
Thanks to a grant from the Mathenaeum Foundation, Girls’ Angle is now in the process of hiring a fulltime Head Mentor for a minimum of twoyears. We are looking for a mathematician who loves to work with K12 students, especially girls.
To give prospective applicants a better idea about the position, the following describes in more depth the educational philosophy of Girls’ Angle and explains the critical role of the Head Mentor.
Girls’ Angle’s approach to math education
We believe that everyone benefits by studying more math, not just those with a special interest in math. Mathematics is a fabulous vehicle for improving one’s ability to think and solve problems, for no other subject shows up errors in reasoning so well. And the best way to obtain these benefits of studying math is to do math.
Consequently, Girls’ Angle welcomes all girls, currently in grades 512, to our club. Our members have diverse relationships to math. Some joined because they love math and can’t get enough of it. Others joined because they feel weak in math but would like to improve. And, yes, there are members who hate math and attend only because their parents want them to. For all these members, we aim to provide a safe, friendly, comfortable environment where they can feel at ease and not selfconscious, so they can focus on math without distraction.
To ensure the best experience for such diversity, our mentors need to be flexible, because what works for one girl may fail miserably for another. Some girls are perfectly happy to be given a challenging math problem and then given lots of space to think on it. Other girls need more guidance. Some members are motivated by competition, others by collaboration. Some members gravitate toward the concrete, while others revel in abstractions. Members have diverse personalities and hold a variety of different interests. Consequently, the stumbling blocks each member naturally encounters in the process of studying math are unique and fascinating. It’s a rich tapestry that also changes with time, even for the same member.
The role of the Head Mentor
Our Head Mentor is responsible for sorting out all this diversity and figuring out what would be best for each member, as an individual, to grow in thinking ability, problemsolving ability, mathematical knowledge, and mathematical understanding as effectively as possible. It is a big job, but it is extremely rewarding, and the Head Mentor has a lot of tools at her disposal to accomplish this task.
The first and most important tool is our group of super mentors, the heart and soul of Girls’ Angle. From the beginning, Girls’ Angle has been blessed with fabulous mentors who are excellent role models. They range from undergraduates majoring in math and related fields, to graduate students in math and related fields, to postdocs in math – each of them possesses strong fundamentals for their respective level in academia. The Head Mentor recruits, coordinates, and works with the mentors to deliver the highest quality math education we can muster.
Second, there is the enormous breadth and depth of mathematics itself. In our view, what is more important than the specific math being studied is to study math in the first place. Rather than insist that a member learn a particular piece of math, we prefer to help a member find some aspects of or problems in mathematics that resonate with her. The beauty of this approach is that mathematics is highly interconnected so that if a person gets hooked on some nice piece of mathematics (and it could be something that is never taught in the standard curriculum), it won’t be long before they branch out and pick up all the standard material. So we have all these members each navigating a unique path through the world of mathematics under the guidance of our mentors, who are, in turn, all coordinated by our Head Mentor.
Should a member become serious about mathematics and begin to contemplate making mathematics a profession, then it does become important for her to develop the discipline to learn important material that may not immediately appeal. When and how to develop this discipline is another matter that the Head Mentor must sort out. Ideally, the student’s own desires provide sufficient motivation to put the nose to the grindstone, but there certainly can be a region of transition.
Why do we need a mathematician for the Head Mentor position?
This is an important question, and one that is not easy to answer completely in a blog post because there are multiple reasons.
Members are a diverse group and represent many different stages in mathematical development. While it is not necessarily immediately appropriate for all members, one of the ideals we aim for is to help members develop into independent and capable thinkers who can solve the yet unsolved. We hope that members who spend some years with us are equipped with the tools and attitude to go into this world and contribute to the solutions to hard problems that have so far stymied us. Solving the unsolved requires creativity, persistence, and an ability to handle psychologically trying conditions. Having tackled unsolved problems and succeeded in creating new mathematics, mathematicians possess these qualities, and because we aim to impart these qualities to our members, we need a Head Mentor who possesses them and knows how to convey them, as well as help and/or facilitate our mentors to do the same.
Often, members don’t yet possess the vocabulary or language skills needed to express their thoughts well, but they do have precious thoughts. Our mentors have to have a radar for member thoughts, however illformed they may be, and be able to encourage them to pursue those thoughts. It may begin with helping a member to sculpt her thoughts into something mathematically actionable, or helping them learn to break a question down into tractable pieces, etc. A mathematician is practiced in this art. What we do not want at Girls’ Angle is for a member to have the inkling of an idea, try to express it, but then somehow lose that thought in the wind.
In fact, this also explains why we need excellent mentors for all our members, whether they excel at math or are floundering. It often takes a great deal of mathematical insight to figure out what a struggling member is having trouble with and how to help the member find a more effective and productive path; and it is so important for struggling members to get fundamentally sound guidance. When a member is bewildered, it does not help for her to have to deal with added layers of confusion created by poor instruction. A mathematician has thought about math to an unusual depth, and with that depth comes greater perspective for the relative importance of various concepts, an understanding of which descriptions of ideas have more generality than others, a knowledge of ideas that may seem expedient but lead to longterm confusion, etc. Our Head Mentor marshals her understanding of math to help our mentors help struggling members in ways that give them the best chance of future success.
At the same time, we need a Head Mentor who knows how to help our members turn their thoughts into theorems. As a concrete example, last year, Allie (we use pseudonyms, which are set in bold font, to refer to our members in public), one of our 6th graders, was playing a dice game we call “Cliffhanger”. This involves the rolling of dice and using the numbers that come up to create an arithmetic expression that evaluates to, or comes close to, a target number. In one round, the dice came up 1, 1, 1, 1, 2, while the target was 34. Allie exclaimed, “There’s no way we’ll be able to make a number that big with all those ones!” Instead of giving hints, the mentor said, “Well, try your best!” While contemplating the challenge, Allie muttered, “What’s the biggest number I can make?” Now there is a mathematical opportunity that must not be ignored! Allie had come up with a mathematical question that is loaded with mathematical potential. So we quickly responded, “Hey, I love that question! I can’t wait to hear your answer.” With encouragement, Allie persisted. From this, Allie managed to formulate the following question: What is the largest number you can express using N ones, addition, multiplication, and parentheses? That became her project for the better part of last year. By midOctober, she had a clear conjecture, but was having great difficulty proving it. Since induction was strongly implicated and induction is an important mathematical proof technique, we took a detour with her and taught her the concept and technique of induction using standard examples and exercises unrelated to her conjecture (such as using induction to prove formulas for the sum of the first n perfect squares, or proving the arithmeticgeometric mean inequality). She eventually had a great handle on the technique and returned to her conjecture. About six meet hours later, she was able to produce a clean, wellorganized, detailed proof, which you can read in our magazine, the Girls’ Angle Bulletin, Volume 11, Number 4, starting on page 22.
There are many other such examples. Math is alive at Girls’ Angle. Mathematics is not a fossilized subject. It is a creative, conceptual art, and our Head Mentor must not only be an ambassador for this art, she must know how to practice it herself and be able to pass this art on to the next generation in an effective way.
Posted in math, Math Education
Tagged Girls' Angle, Girls' Angle Bulletin, Head Mentor, math education for girls
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Girls’ Angle Bulletin, Volume 11, Number 4
The electronic version of the latest issue of the Girls’ Angle Bulletin is now available on our website.
Betsy Stovall, assistant professor of mathematics at the University of WisconsinMadison, kicks off Volume 11, Number 4 with a wonderful interview. Her story of how she became interested in math is inspiring. She also describes one of the nifty problems that sparked her interest in math when she was a student. If you haven’t seen it before, it’s well worth thinking about.
Deanna Needell adds a second installment to her column The Needell in the Haystack, this time about filling in missing entries of a matrix. She describes an application to the study of Lyme disease. To fully understand Prof. Needell’s articles, one does have to be familiar with matrices. For those of you who don’t know about matrices, we included a very brief introduction to matrices intended to help reader’s unacquainted with the concept at least feel good enough about them to read Prof. Needell’s Bulletin contributions. Her articles are very much worth reading even if you don’t know about matrices.
Emily and Jasmine embark on a new adventure resulting from a graphic design project themed on the circle. The assignment inspired Emily to create a design of radiating circles. To create the design, she discovered some neat math. This new journey was inspired (in a somewhat indirect way) by work of students at the Buckingham, Browne, and Nichols Middle School.
Anna makes progress on her current problem by characterizing those for which is congruent to 1 modulo 3.
Lightning Factorial authors an installment of Math In Your World, analyzing how to intercept an incoming tennis shot as quickly as possible.
Next, Girls’ Angle member Allie presents her wonderful inductive proof of a conjecture she came up with at the Girls’ Angle club regarding the largest number expressible using N ones, addition, multiplication, and parentheses.
We round out the issue with some Notes from the Club.
We hope you enjoy it!
Finally, a reminder: when you subscribe to the Girls’ Angle Bulletin, you’re not just getting a subscription to a magazine. You are also gaining access to the Girls’ Angle mentors. We urge all subscribers and members to write us with your math questions or anything else in the Bulletin or having to do with mathematics in general. We will respond. We want you to get active and do mathematics. Parts of the Bulletin are written to induce you to wonder and respond with more questions. Don’t let those questions fade away and become forgotten. Send them to us!
We continue to encourage people to subscribe to our print version, so we have removed some content from the electronic version. Subscriptions are a great way to support Girls’ Angle while getting something concrete back in return. We hope you subscribe!