## Girls’ Angle Bulletin, Volume 10, Number 3

Volume 10, Number 3 opens with an interview with Sommer Gentry, professor of mathematics at the US Naval Academy. Prof. Gentry invented a system for optimizing kidney transplantation that positively. This interview was conducted by Girls’ Angle progam assistant Long Nguyen. As has been our practice, we truncate the interview in the electronic version. For the full version, please subscribe!

Next comes Villanova assistant professor of mathematics Beth Malmskog‘s concluding part of Quilt-Doku! Here she shows that a 5 by 5 row complete Latin square is impossible. Shown at right is a row complete Latin square of order 15. It remains an unsolved problem to determine if there are any row complete Latin squares of odd prime order.  In fact, it isn’t even known that there isn’t one of order 13. Can you prove it?

Test your area computation skills in Area Area. Can you solve these area problems in your head?

Anna B. continues to search for a combinatorial proof that the conjectured formula she found for the number of special tilings of a 1 by $\sqrt{2}$ rectangle is, in fact, valid. She remains stumped. Can you help her prove that the close-form formula she found is correct?

Emily and Jasmine continue their pursuit of triangles with 3 nice angles but only 2 sides of integer length at Cake Country where they run into Alison Miller, a Benamin Peirce and NSF Postdoctoral Fellow at Harvard University. Prof. Miller gives them a lot to chew on for next time! She also mentions Gauss’s Lemma, but doesn’t have time to prove it, so we provide an installment of Learn by Doing where you can prove the lemma for yourself.

The cover pertains to Addie Summer’s follow-up to her article on the quadratic formula. In this issue, she creates a graphical representation of monic quadratics and interprets properties of them geometrically. On the cover, the surface represents monic cubics with multiple roots. Specifically, it is the surface of points (bcd) in bcd-coordinate space such that the cubic $x^3 + bx^2+cx+d$ has multiple real roots. (Note that if a cubic with real coefficients has multiple real roots, then all of its roots are real.) This graph was created using MATLAB, a powerful suite of math software created by MathWorks. MathWorks has been a valuable sponsor of the Girls’ Angle Bulletin for several years.

For fun, we offer a self-referential true/false quiz that was inspired by a self-referential multiple choice test created by Jim Propp.

Finally, we conclude with Notes from the Club, which contains a description of one of our more versatile and popular games: Describe that Drawing.

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!