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chris_wot

Nice! They should use this in schools.

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Some do, that's how I learned them.

edit: I still think the most confusing thing about radians when learning them is the 2 pi. This seems so arbitrary.

We now use Tau at work and it makes everything easier to understand.

You use τ where you work? Where do you work (in general terms)?

Why arbitrary? C=2pi*r. It's degrees that are arbitrary.

C = tau * r. Why divide the circle in half?

C = pi * D

where D = 2r

I prefer "pau". http://xkcd.com/1292/

lol. I always wonder how people find these things.

Incidentally, I recently read an article about how the creators of The Simpsons actually held math degrees. They hid mathematical easter-eggs all over their episodes. One gag was a "solution" to Fermat's last theorem where 1782^12 + 1841^12 = 1922^12. It's valid up to like, the twelfth significant digit.

It's even more funny when you know that "pau", in Catalan, means "peace".

A = 2taur^2. Why divide the circle in half?

The early use of pi was calculating area and it was derived based on that. At least as far as history can tell us. Records are a little sketchy that far back.

The argument in favour of tau in the formula for the area of a circle is this: To find the area of a circle with radius r, you integrate the circumference of every circle with radius between 0 and r. The integral of tau*r with respect to r is 1/2 tau r^2. Since 1/2 ax^2 is such a common form when dealing with integrals, it can be easier to remember this way.

That's a weak argument. Integrating 2a * x is also insanely common in dealing with integrals. And really if you're deriving the area of a circle and integrating 2pi * r gives you pause you're not on a good road to begin with and removing a 2 from some equations isn't going to help much.

edit: forgot that * would make everything italicized.

Good. Now try sphere surface.

Sure...

Sphere surface area: 4pi * r^2

Sphere volume: (4/3) * pi * r^3

Both would still have a coefficient if tau replaced pi...

You aren't diving the circle in half, you are using the radius. Radius vs arc length makes perfect sense; diameter vs arc length doesn't.

Which is why tau is a better constant to use than pi.

Think of it as radiUS and radiAN, the AN being angle. Since there is PI angle in a radius, there has to be 2PI in a diameter since d=2r.

> Since there is PI angle in a radius

The only part that doesn't make sense.

His comment took me a while to parse too. The way I ultimately interpreted his comment was "Since 1(d) = 2(r), it's only natural that 1(rotation) = 2(PI radians)". Which is ironic. I.e. the inequality between the coefficients is actually the tau-ists' primary argument against pi. Also, I don't know how it's relevant to its parent comment, which was about "1 rotation being defined as 360 degrees" being arbitrary.

The 360 isn't arbitrary, rather boils down to 60 arc-minutes and 60 arc-seconds, which of course is 3600 arc-seconds in circle. Where the 60 comes from:

http://mathforum.org/library/drmath/view/65468.html

Wouldn't surprise me if the minutes and seconds relates to navigation time in the past.

We do. And silly songs on YouTube. And any other good content people want to make.

This being HN, how about someone whipping up a Web application where teachers can post 'want ads' for small things like this and creative visual people can respond by posting links to bits of work? For the lutz and to help?

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