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)