## Girls’ Angle Bulletin, Volume 10, Number 1

Volume 10, Number 1 opens with an interview with Dr. Brandy Wiegers, an assistant professor of mathematics at Central Washington University and associate director for the National Association of Math Circles.  This interview was conducted by Girls’ Angle summer intern Sandy Pelkowsky. As has been our practice, we truncate the interview in the electronic version. For the full version, please subscribe!

The cover features an image of an opened Quintetra assembly by Jane and John Kostick. Jane visited Girls’ Angle last month and led the girls in an exploration of tetrahedra, cubes, and rhombic dodecahedrons. For more on the Quintetra assembly, please see Volume 7, Number 4 of the Girls’ Angle Bulletin.

After the interview, we offer 3 theorems to meditate upon in Meditate to the Math. All 3 theorems involve the construction of dropping a perpendicular from a point to a line, and, although it might be a challenge, all 3 theorems can reasonably be proven without use of scratch paper – just sitting comfortably, observing, thinking, meditating.

Next up is the concluding half of Prof. Helen Wilson‘s article on chocolate flow. This half is considerably more mathematically involved than the first half. In it, Prof. Wilson gets into the details of scaling analysis by leading us through an example involving liquid chocolate. It’ll help if you’re familiar with calculus. Just don’t be intimidated by the big partial differential equations that govern fluid flow! The whole point of the article is to show how to tame such a massive equation.

Emily and Jasmine return to their pursuit of triangles with 3 nice angles but only 2 sides of integer length. They decide to embark on an investigation of the minimal polynomials of cosines of nice angles.

Anna B. follows through on a question that sprouted up in the last issue: how many special N-tilings are there of a 1 by $\sqrt{2}$ rectangle?

Addie Summer goes crazy (well, in a way) and counts some familiar sets in a complicated way, and is rewarded with beautiful identities involving binomial coefficients.

We conclude with Notes from the Club, featuring just a few of the things that have been happening at the Girls’ Angle club so far this semester.

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!