The latest issue of the Bulletin is now available. The Girls’ Angle Bulletin has faithfully come out at the end of every even-numbered month for four full years! That’s over 700 pages of math.

The cover illustrates the fact that if you take any parabola with a vertical axis and walk from the vertex in a southwest-northeast direction, when you meet the parabola again (if you meet it again!), the tangent line at that point will have slope exactly 2.

A frame from the Girls' Angle video demo, The Ball and The Parabola, by Hana Kitasei and Gabriela Acevedo

I thought a parabola design would be appropriate since quadratic functions appear in this issue’s *Mathematical Buffet*, *Anna’s Math Journal*, Cammie Smith Barnes’ *Errorbusters!*, *Picturing Quadratics*, and Rachel Fraunhoffer’s Summer Fun problem set solutions.

Also inside, read the concluding half of our interview with Brown University Tamarkin Assistant Professor and Girls’ Angle advisor and mentor Bianca Viray, a number theorist who received her doctoral degree in mathematics from UC Berkeley under the supervision of Girls’ Angle advisor and MIT Professor Bjorn Poonen.

From Summer Fun solutions.

Mathematician Timothy Chow explains the meaning of “Without Loss of Generality” in his characteristically clear prose. This is Tim’s second article for the Girls’ Angle Bulletin. His first article, *What is Proof?*, appeared in Volume 1, Number 5. For more advanced readers, I highly recommend his article *A Beginner’s Guide to Forcing*, which serves as a great first read to learning about Paul Cohen’s proof of the independence of the continuum hypothesis.

Katherine Sanden follows up on her article about social networks and graph theory with an article about six degrees of separation. In mathematical circles, this concept is related to the “Erdös Number.”

From Coach Barb's Corner

Barbara Remmers writes about another conic section, the circle, in *Coach Barb’s Corner*. If you like the circular arrangements in this article, you might enjoy reading about Apollonian circles, of which Katherine Sanden is something of an expert having written her senior thesis at Princeton about them.

From Summer Fun Solutions

And finally, there are the solutions to last issue’s Summer Fun problem sets.

Hope you enjoy it and feel free to suggest topics for articles you’d like to see in the future! If you like the Bulletin, please show your support by becoming a Bulletin Sponsor.

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