## Girls’ Angle Bulletin, Volume 11, Number 6

It’s always nice to hear from old friends. Katy Cook née Bold was the first author for Math In Your World, a column about applied math. She contributed 8 installments before turning over the reins to Katherine Sanden. The cover features a rug that Katy designed together with Sara Eizen. What’s its mathematical significance? If you’ve made a math-themed carpet, we’d love to see pics. If we get enough, we’ll devote an installment of Math Buffet to them.

Rachel Pries gives us a wonderful interview for this issue. Rachel is a Professor of Mathematics at Colorado State University and received her doctoral degree in mathematics from the University of Pennsylvania under the supervision of David Harbater. Also, she is an alumna of Cambridge Rindge and Latin, which is just down the road from Girls’ Angle.

Next up, the fourth installment in Deanna Needell‘s series The Needell in the Haystack, about big data algorithms. Big data generally means high dimensions. For example, a very small 100 pixel by 100 pixel image can be thought of as a vector in a 10,000-dimensional space. In this installment, Deanna explains an unintuitive feature of high-dimensional spheres.

Addie Summer gives us an example of how she entertains herself in idle moments with mathematics in Systematic Counting, Part 1.

Then, we follow Emily and Jasmine on their continuing exploration of stacked circles. This time, their on a quest for stacked circles whose radii form a harmonic progression, but they run into a massive snag.

We conclude with solutions to the four Summer Fun problem sets of the previous issue. The best way to learn math is to do math, and tackling math problems is a good way to start doing math. But also, tackling math problems is a good way to develop your problem-solving skills. There is so much more to math problem-solving than being familiar with mathematics. I have seen students who know all the math involved with a particular problem, yet fail to solve the problem because of organizational issues. There are also psychological factors to learn to deal with. I don’t know how many times I’ve seen, and been victim to, an unwillingness to explicitly work out the simplest case of something, thinking that it is too trivial to pay attention to, and have that turn out to be a key obstacle. Once the reluctance is overcome and the seemingly trivial example is carefully worked out, the solution to the rest suddenly appears.

Special thanks to our four 2018 Summer Fun contributors, Matthew de Courcy-Ireland, Laura Pierson, Whitney Souery, and Vicky Xu!

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!