## Girls’ Angle Bulletin, Volume 5, Number 6

The electronic version of the latest issue of the Girls’ Angle Bulletin is now available on our website. This issue represents 5 years of the Bulletin, which has come out on the last day of every even-numbered month since October of 2007!

In that span of time, dozens of contributors have contributed articles, there have been 5 batches of Summer Fun problem sets, descriptions of math activities and games, and interviews with 17 women in mathematics including the first women tenured at both Princeton (Ingrid Daubechies) and Harvard (Sophie Morel). We’re making a big push to increase the circulation of our print edition and we hope you consider subscribing. For \$36/year you get 6 printed issues and access to our mentors via email. Unlock the power of problem solving…subscribe and master mathematics!

This image under the hyperbolic cosine function didn’t make it into the magazine. See the Mathematical Buffet for details on how these images were made.

Mathematical Buffet

The cover of our latest issue shows the image of a square grid in the complex plane under a conformal transformation. More such images comprise this issue’s Mathematical Buffet. All of these images have the same domain in the complex plane. We give the exact transformations, but encourage readers to figure out which transformation corresponds to which image. Doing so is a great exercise if you are beginning to learn about complex numbers. We used MATLAB, a powerful suite of mathematical software produced by MathWorks, to create these images.

Jean Pedersen, Part 3.  The third and final part of our interview with Santa Clara University professor of mathematics Jean Pedersen opens the latest issue. Thank you, Dr. Pedersen, for this wonderful interview!

Sprint Track Cycling. With this issue’s Math In Your World, columnist Katherine Sanden turns over the reigns to Princeton alumnus Taotao Liu. Katherine has decided to devote more time to her music/video projects. We especially like her Complex Analysis Rap! We’re going to miss her contributions and we wish her success!

Taotao demonstrates some game theoretic thinking and then applies it as best possible to explain otherwise bizarre behavior in sprint track cycling, an Olympic racing event where extremely strong cyclists can be found at times trying their best to go as slow as possible!

Anna tries, but fails, to explain the mystery of the zeroes that she conjectured in her last installment. Can you help her to resolve this mystery? If you haven’t been keeping up with her latest explorations, you’ll need to catch up by going back to the October, 2011 issue.

Errorbusters! Cammie cautions us about accidentally tossing away zero solutions to polynomial equations and, at the same time, provides a quick tour of some of the fundamental concepts and facts associated with one-variable polynomials.

Coach Barb, or, I should say, 3/7, brings the joy of ratios to our lives, served with a side of shortbread cookies. This is the 6th installment in her series on Fraction Satisfaction, and she has covered a lot of ground. If you fear fractions, I urge you to read this series from the beginning.

And finally, there are the Summer Fun solutions to the Summer Fun problem sets in the previous issue. These problems span an enormous range in difficulty levels. There are even some problems that will challenge college math majors, like this problem from 3/7′s evil twin 7/3: Let $a_1 = a_2 = 1$. Recursively define $a_{n+1} = \frac{1}{a_n + a_{n-1}}$ for $n > 2$. Prove that this sequence has a limit. What does it converge to? (If you assume the sequence has a limit, one can readily determine what this limit is. The more challenging part is to prove that the sequence does converge.)

If you had trouble with any problem, don’t fret. Just write to us (if you’re a subscriber) and we’ll help!

Hope you enjoy it!