## A Tau-stimonial

Hiya, Dr. Hartl.

I’ve been a fan of *The Tau Manifesto* for quite a while, I ordered the
Tau Day t-shirt, etc. And today I come to you with a $\tau$ success story.
I hope it warms the cockles of your heart as it did mine.

I’m an undergraduate student, and I spent the just-recent spring break
with my family. During my stay, my 15-year-old sister begged me for
help on an upcoming trigonometry test, which was based primarily on
converting between degrees and radians and finding sines and cosines
of all manner of wacky angles. She gave me a bundle of homeworks (all
with fairly depressing scores) that showed the material covered.

I started off trying to reinforce some of the concepts she seemed to
be confused about, but she said I mostly ended up echoing her teacher
and that she still just “wasn’t getting it.” So I said to myself,
“screw this, I’m going to do this the Correct Way,” and I started
teaching her all of the same material from scratch, but using $\tau$
instead of $\pi$. Just as I was drawing the fractional segments of a
circle labeled with $\tau$, $\tau/2$, $\tau/3$, etc., her eyes lit up—she
*grokked* it. And when I drew the first right triangle to talk about
sines and cosines, she took the pencil from me and finished explaining
the material herself. And then she went back and annihilated all the
old homework problems she missed.

Her strategy for the test was to do every problem with the $\tau$-circle,
and then to sweep over it at the end and convert every $\tau$ to $2\pi$. She
was the first one in her class to finish the test, with a 100%.

So I (and my little sister) thank you, Dr. Hartl, for campaigning as
avidly as you have for $\tau$. It has enriched our lives and brought us
much joy, and will probably stop the End of Days. Keep up the good
fight; I intend to as well, where I can.

—an MIT undergraduate (who wishes to remain anonymous)