### Author Topic: Happy PI day (a day late) and a question  (Read 1343 times)

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#### dsharp02

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##### Happy PI day (a day late) and a question
« on: March 16, 2016, 02:58:14 am »
Was reading this:  http://tauday.com/

and it got me thinking about RC time constants and how tau is used as a shorthand.

If the Tau-ists had their way calculating cutoff frequencies for RC filters could get really confusing.

Fc = 1 / (2 * pi * R * C)
(substituting tau, the RC time constant) =>   Fc = 1 / (2 * pi * tau)
(substituting tau, the mathematical constant) => Fc = 1 / ( _tau_ * tau)

So I guess the question is tau? or pi?

#### ericloewe

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##### Re: Happy PI day (a day late) and a question
« Reply #1 on: March 16, 2016, 05:01:54 am »

Pau = 1.5 * pi is the way to go. It'll please nobody, so nobody will feel left out.

Notice how next to nothing is abbreviated with the letter pi. Since pi has been the traditional constant used, everything else more or less decided not to use the letter pi. Had tau been the "one true constant", I'd expect the opposite to happen - the letter tau practically reserved for 2pi and the letter pi more or less free to use in most contexts.

#### TimFox

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##### Re: Happy PI day (a day late) and a question
« Reply #2 on: March 16, 2016, 08:19:01 am »
I like "pi" because of the Euler equation: [ e ^ (i pi) ] + 1 = 0.
This simple equation contains e, i,  pi, 1, and 0 -- truly fundamental constants.

#### IanB

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##### Re: Happy PI day (a day late) and a question
« Reply #3 on: March 16, 2016, 08:30:10 am »
It only needs one sign change: $e^{i\tau} - 1 = 0$
I'm not an EE--what am I doing here?

#### ericloewe

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##### Re: Happy PI day (a day late) and a question
« Reply #4 on: March 16, 2016, 08:42:37 am »
Congratulations. You just proved that "pi vs tau" is an equivalent(ly silly) discussion to "plus vs minus".

#### Cerebus

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##### Re: Happy PI day (a day late) and a question
« Reply #5 on: March 18, 2016, 10:40:46 am »
I like "pi" because of the Euler equation: [ e ^ (i pi) ] + 1 = 0.
This simple equation contains e, i,  pi, 1, and 0 -- truly fundamental constants.

So, we have pi day. Why not "e day" and "i day"? The latter I propose belongs on the 29th of February.
Anybody got a syringe I can use to squeeze the magic smoke back into this?

#### ericloewe

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##### Re: Happy PI day (a day late) and a question
« Reply #6 on: March 18, 2016, 11:01:45 pm »
I like "pi" because of the Euler equation: [ e ^ (i pi) ] + 1 = 0.
This simple equation contains e, i,  pi, 1, and 0 -- truly fundamental constants.

So, we have pi day. Why not "e day" and "i day"? The latter I propose belongs on the 29th of February.

Because it only happens once every four pi/2?

Smf