# Half Tau Day is Fast Approaching!

Hello all! I hope you're all gearing up for $$\frac{\tau}{2} = \pi$$ day! I am a giant proponent of $$\tau$$, and you should be too. For those of you who don't know, $$\tau = 2\pi$$. $$\tau$$ is a much more natural circle constant, as a circle is, after all, defined by its radius, not its diameter. One can find an incredibly compelling argument for $$\tau$$ in Michael Hartl's Tau Manifesto. I know I'll be spending Half Tau Day unwillingly participating in $$\pi$$ activities with my blissfully ignorant peers, who I will inevitably urge to join Brilliant and educate themselves about the marvels of $$\tau$$!

Have a safe and happy $$\frac{\tau}{2}$$ day!

Note by Ryan Tamburrino
3 years, 7 months ago

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To be honest they are equally valid, as $$\pi$$ is better in some situations and $$\tau$$ is better in others. For example: circumference = $$\tau$$r may be easier to deal but then you end up with an area of: $$\frac{\tau}{2}$$$$r^{2}$$. You may also look at it from a trigonometry point of view... all the trigonometric functions repeat themselves every $$\tau$$ radians, but then when proving that $$\zeta$$(2) = $$\frac{\pi^2}{6}$$ you need $$\pi$$to obtain: $\frac{sin(x)}{x} = \displaystyle\prod_{n=1}^{\infty} (1-(\frac{n\pi }{x})^2)$ and the argument continues....

- 3 years, 7 months ago

I will concede a few small victories to $$\pi$$, including that one that you mentioned regarding the $$\zeta$$ function. However, if you look at the Tau Manifesto, Hartl shows that area of a circle with $$\tau$$ follows other quadratic forms of other formulas from physics. So, that $$\frac{1}{2}$$ out in front isn't quite as unnatural as it seems.

- 3 years, 7 months ago

Maybe there ought to be a friendly Tau vs pi debate

- 3 years, 7 months ago

I feel stupid for asking this but isn't $$\pi$$ day on $$14$$ March?

- 3 years, 7 months ago

Yeah! This $$\pi$$ day is special though, because it will be (in the American format of month/day/year) $$3/14/15$$. $$\tau$$ will have its revenge on $$6/28/31$$!

- 3 years, 7 months ago