## Girls’ Angle Bulletin, Volume 11, Number 3

Can you figure out what the cover represents?

Volume 11, Number 3 kicks off with an interview with Rhonda Hughes, Professor Emeritus of Mathematics at Bryn Mawr College. In it, Prof. Hughes describes one of the most interesting paths into mathematics, and she gives lots of good advice to students.

Next up is the concluding half of Partitions from Mars, by Pamela E. Harris, Alexander Pankhurst, Cielo Perez, and Aesha Siddiqui. They conclude with an open problem about partition functions. Can you solve it?

Last issue, we interviewed UCLA Professor of Mathematics Deanna Needell. In this issue, Prof. Needell returns with a nifty article on topic modeling, explaining the technique of non-negative integer matrix factoring. Every day, people produce something on the order of $10^{19}$ bytes of data every day, and this rate is accelerating. But all this data is useless if we don’t have the tool to extract information from it. In The Needell in the Haystack, Prof. Needell shares with us her expertise and teaches us the basics of large-scale data analysis.

Anna’s Math Journal returns after a brief break to tackle a question about numbers formed by interpreting rows of Pascal’s triangle, modulo 3, as ternary numbers. Specifically, in the resulting sequence, which numbers are odd? Computing how many of the first 2018 of these numbers are odd was a problem at SUMIT 2018, a big math event we ran at the Broad Institute earlier this month.

In Errorbusters! we discuss a powerful way to minimize numerical computation errors: use variables. The use of variables delivers several benefits besides just reducing the number of dicey numerical computations. We illustrate by tackling problem 15 from the 2017 AIME I contest.

I’ve now been working with students on math for decades, and sometimes, I meet students who treat all facts equally, as if each were another isolated item to learn about this world we live in. But what is amazing about math is that some facts follow logically from others. Building connections between facts through implication enables us to understand a lot with little knowledge and helps us to retain facts because we can then understand them from many angles. To progress in mathematics, it is crucial to understand this. So I tried to address it directly with the article Implications.

We conclude with a Learn by Doing problem set on Fibonacci numbers, a note on the notation used for functions, and 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!