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Happy Phi Day!
Posted by Nick on 18 June 2000, 08:07 GMT

Today, June 18, is Phi Day. As Daniel Bishop pointed out, Phi is an irrational number, not unlike Pi. Approximately equal to 1.61803398874989484820458683436564 (today is June 18 - 6/18 - har har har), Phi is used a great deal in astronomy. Most importantly, it's found in the proportions in the Greeks' famous golden rectangle. It's deriveable by many proofs, including the famous Fibonacci Sequence (one of my personal favorite series, if there even is such a thing). For more information on Phi, click here and here.

 


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Re: Happy Phi Day!
matt c  Account Info
(Web Page)

why does phi day gotta go and steal my birthday?
thats not cool. oh well.
how come ive never heard of phi before

     19 June 2000, 04:19 GMT

Re: Happy Phi Day!
Sesquipedalian

As the original news item said, phi is irrational, but it _is_ unlike pi in an important way: pi is trancendental, while phi is not. That interesting sounding word actually has a precise mathematical meaning, which is this: a number is trancendental if it is not the root of any polymonial with integer cooeficients. phi, as you can see in a few other peoples' comments is the root of a rather simple quadratic equation, so is not trancendental. pi has been proven to be trancendental, as has e. Unfortunately, I can't give you links for the proofs, but you can probably find them without too much effort.

     19 June 2000, 04:37 GMT

Re: Re: Happy Phi Day!
mysteryegg  Account Info
(Web Page)

That's okay... about a month ago, somebody proved that e^(i*pi)=-1

     19 June 2000, 16:22 GMT

Re: Re: Re: Happy Phi Day!
Sebastian Reichelt  Account Info
(Web Page)

Must have been a lot earlier. That equation is even programmed into the TI-89.

     19 June 2000, 19:10 GMT


Re: Re: Re: Happy Phi Day!
Scott Dial
(Web Page)

e^(i*u)
cos(u)+sin(u)*i

Let u = pi:
cos(pi)+sin(pi)*i
-1 + 0 * i
-1

Relatively simple proof...

     9 October 2001, 01:31 GMT


Re: Re: Happy Phi Day!
Ryan Castellucci  Account Info

Pi can be written is sigma notation. i froget how. here's why:
pi=4(1/1-1/3+1/5-1/7+1/9-1/11...)
Someone figure out how to put that in sigma.
_\ / |)
|otta|)yte

     20 June 2000, 21:17 GMT


Re: Re: Re: Happy Phi Day!
BudIcePenguin Account Info

After a bit of testing...

? = 4 * (1?n??)? [((-1)^(n-1))÷(2n-1)]

it takes a fairly large value to get an accurate approximation tho (use the sum seq() on a TI-86)

     17 December 2003, 20:36 GMT

Re: Stupid Phi Day!
David  Account Info
(Web Page)

These Pi, Phi, etc. days are, well, kind of STUPID. This is not a flame, it is my opinion. Really, what's the point in having a Phi day?

     19 June 2000, 17:14 GMT


Re: Re: Stupid Phi Day!
JaggedFlame

What's the point of NOT having a Phi day? ;-P

     19 June 2000, 18:17 GMT


Re: Re: Re: Stupid Phi Day!
Chris Moultrie  Account Info
(Web Page)

Hey, pi day gave us a reason not to have class but to have a pi party in class...why not have a chance for a party in summer school?

     20 June 2000, 01:45 GMT

Re: Re: Re: Re: Stupid Phi Day!
The_Professor  Account Info
(Web Page)

Summer School!!!!!!µ¥¦½¼¾ßø²ª®§!!!... I would think that anyone that would celibrate Phi day, pi day, or other mathematical constant days wouldn't have to go to summer school... except, of course, for people that attend those college 'summer sesions'... or whatever they're called...

And hopefully nobody is STILL going to school... my school year ended early {for me} this year on May 31... (a week late because of snow days, but still early...)

     20 June 2000, 03:48 GMT


Re: Re: Re: Re: Re: Stupid Phi Day!
Daniel Bishop  Account Info
(Web Page)

My last day of high school was May 19. Of course, there are no snow days here in the Houston area.

     20 June 2000, 19:42 GMT


Re: Re: Re: Re: Stupid Phi Day!
Daniel Bishop  Account Info
(Web Page)

Pi Day was never celebrated at my high school because it's always during spring break.

     20 June 2000, 19:39 GMT

Re: Happy Phi Day!
Daniel Bishop  Account Info
(Web Page)

Don't forget:

2Pi Day: June 28
Pi Approximation Day: July 22
g Day: September 8
c Day: October 8
Metric Day: October 10
Mole Day: October 23
i Day: February 30
Pi Day: March 14

Does anyone know of any other number days? It's possible that mathematicians and physicists have created more "holidays" than Hallmark.

     19 June 2000, 20:19 GMT

Re: Re: Happy Phi Day!
Sean Kinney  Account Info

So. Should I bring cake and cookies to Calculus on those days?

     20 June 2000, 01:25 GMT

Re: Re: Happy Phi Day!
Grant Elliott  Account Info
(Web Page)

42 Day: Apr 2

     20 June 2000, 02:52 GMT

Re: Re: Happy Phi Day!
The_Professor  Account Info
(Web Page)

Well, I am not sure but I think that e day should be July 18... {7.1828182845....}

     20 June 2000, 03:53 GMT


July 18
Daniel Bishop  Account Info
(Web Page)

e = 2. 718 281 828 459 045 235 360 287 471 352 66

which is not at all close to 7.1828182845. The number you posted is 10(e-2).

btw, did you know that July 18 is the anniversary of the assasination of Czar Nicholas II?

     20 June 2000, 19:37 GMT


Re: July 18
The_Professor  Account Info
(Web Page)

Oh... whoops... Well, at least the digits weren't wrong {except for what you mentioned, of course}...

And I still think that e-day should be on July 18

e ~ 2.718281828459045235 36028747135266249775 72470936999595749669 67627724076630353547...

{and this time it is right}...

     20 June 2000, 20:23 GMT

Re: Re: Happy Phi Day!
The_Professor  Account Info
(Web Page)

How about the absolute value of i day - January 1
Or the real part of the squareroot of i {.7071067811865...} day - July 7

     20 June 2000, 20:41 GMT


Re: Re: Happy Phi Day!
Ryan Castellucci  Account Info

ohhhh! my bitrhday is g day!

_\ / |)
|otta|)yte

     20 June 2000, 21:11 GMT

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