# A few questions about pi **URL:** \ **Category:** Factual Questions\ **Created:** [September 29, 2004, 11:34pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757 "2004-09-29T23:34:44Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![suranyi](https://avatars.discourse-cdn.com/v4/letter/s/e36b37/32.png) [@suranyi](https://boards.straightdope.com/u/suranyi)\ **Post date:** [September 30, 2004, 6:18pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/21 "2004-09-30T18:18:44Z")
> [@ITR champion](#): > > The fact that such a constant as pi existed was known long before Archimedes, who lived at the time of the Punic Wars. The Ancient Egyptians and Ancient Babylonians both attempted to calculate pi by the method of inscribing a regular polygon inside a circle and then adding up the lengths of the sides. The more sides the ploygon had, the better the estimate they got. . What Archimedes definitely did do first was show that pi was also the proportional constant between the square of the radius and the area of the circle. It had long been known that the area of a circle was proportional to the square of the radius, but he showed that the constant was the same as that which connected the diameter to the circumference. Ed ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [September 30, 2004, 6:33pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/22 "2004-09-30T18:33:26Z")
Here’s one I like: The infinite product (2/1)(2/3)(4/3)(4/5)(6/5)(6/7)(8/7)(8/9)… converges to pi/2. I second **js\_africanus** ’s recommendation of _A History of Pi_. ---
**Author:** ![Charlie\_Tan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/charlie_tan/32/12582_2.png) [@Charlie\_Tan](https://boards.straightdope.com/u/Charlie_Tan)\ **Post date:** [September 30, 2004, 8:16pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/23 "2004-09-30T20:16:06Z")
Would it be possible to assume that π =1 and make all other numbers fractions of π? Well possible, of course, since I just assumed it, but could it serve any pratical or theoretical purposes? ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [September 30, 2004, 8:17pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/24 "2004-09-30T20:17:51Z")
> [@The Gaspode](#): > > Would it be possible to assume that π =1 and make all other numbers fractions of π? Well possible, of course, since I just assumed it, but could it serve any pratical or theoretical purposes? Possible, but why? ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [September 30, 2004, 8:19pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/25 "2004-09-30T20:19:56Z")
Strike that. pi = 1 can’t be done because pi is not a multiplicative identity. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [September 30, 2004, 9:08pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/26 "2004-09-30T21:08:36Z")
But you _could_ make a number system of base-pi, right? That way, pi would be 10. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [September 30, 2004, 11:57pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/27 "2004-09-30T23:57:46Z")
> [@ultrafilter](#): > > Strike that. pi = 1 can’t be done because pi is not a multiplicative identity. Well, you _could write_ numbers that way—just write x/pi in place of x—but they’d be confusing-as-all-get-out to work with because, as you note, the multiplicative identity would not be the number written “1” but the number written “1/pi.” It’s already common in certain contexts to write angles as fractions of pi (e.g. pi/6 = 30 degrees, pi/4 = 45 degrees, 2pi = 360 degrees). ---
**Author:** ![js\_africanus](https://avatars.discourse-cdn.com/v4/letter/j/87869e/32.png) [@js\_africanus](https://boards.straightdope.com/u/js_africanus)\ **Post date:** [October 1, 2004, 4:28am UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/28 "2004-10-01T04:28:34Z")
> [@CurtC](#): > > But you _could_ make a number system of base-pi, right? That way, pi would be 10. I don’t think so. But I’m not sure. Pi is irrational and that is independent of what base you put it in. I think. > [@Thudlow Boink](#): > > It’s already common in certain contexts to write angles as fractions of pi (e.g. pi/6 = 30 degrees, pi/4 = 45 degrees, 2pi = 360 degrees). Well, not really. (pi/6) is a certain number of _radians_, so you have degrees being converted into radians because they’re better to work with mathematically. (Hence the _Fox Trot_ where the kid said that golf would be easier if distances and angles were in metric & radians instead of English & degrees.) One radian is the angle described by an arc equal in length to the radius of the circle, and since 2pi\*r is the circumference (sp?), the number of radians in a circle equals 2pi. Since pi is irrational, I think that if you somehow set it to be you basic unit, other stuff wouldn’t work out right and you’d have a whole mess. Borrowing a description of the hypoteneus of a right triangle that I once read, there is no measuring unit that you can use to measure the radius of a circle in whole units that will also measure the circumference in whole units. So if you set a unit equal to one circle circumference, there’s no way you could get a sensible unit for the radius. I think. I better shut up and let the more knowledgeable actually drop some phat mathematics before stupidify the place too much. ---
**Author:** ![ccwaterback](https://avatars.discourse-cdn.com/v4/letter/c/df705f/32.png) [@ccwaterback](https://boards.straightdope.com/u/ccwaterback)\ **Post date:** [October 1, 2004, 6:57am UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/29 "2004-10-01T06:57:22Z")
My favorite? gamma(1/2) = sqrt(pi) [http://www.sosmath.com/calculus/improper/gamma/gamma.html](http://www.sosmath.com/calculus/improper/gamma/gamma.html) ---
**Author:** ![Sublight](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@Sublight](https://boards.straightdope.com/u/Sublight)\ **Post date:** [October 1, 2004, 8:41am UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/30 "2004-10-01T08:41:28Z")
> [@Peter Morris](#): > > Every time I need pi accurate to 7 decimal places I simply recite **"May I have a large container of coffee."** If you ever need to remember pi to 740 places, just start reciting… [Poe. E. Near a Raven. Midnights so dreary, tired and weary, Silently pondering volumes extolling all by-now obsolete lore. During my rather long nap - the weirdest tap! An ominous vibrating sound disturbing my chamber’s antedoor. “This”, I whispered quietly, “I ignore”…](http://users.aol.com/s6sj7gt/mikerav.htm) ---
**Author:** ![umop\_ap\_sdn](https://avatars.discourse-cdn.com/v4/letter/u/dbc845/32.png) [@umop\_ap\_sdn](https://boards.straightdope.com/u/umop_ap_sdn)\ **Post date:** [October 1, 2004, 8:43am UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/31 "2004-10-01T08:43:43Z")
Sir, I send a rhyme excelling In sacred truth and rigid spelling. Numerical sprites elucidate For me the lexicon’s dull weight. ~or~ See, I send a rhyme assisting My feeble brain, its tasks oft resisting. Not as many digits as **FlippyFly** ’s or **Sublight** ’s, but it’s a helpful mnemonic. ---
**Author:** ![Cabbage](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@Cabbage](https://boards.straightdope.com/u/Cabbage)\ **Post date:** [October 1, 2004, 10:15am UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/32 "2004-10-01T10:15:00Z")
**Sublight** , that work has been [extended](http://users.aol.com/s6sj7gt/cadtext.htm) by the same author to about 4000 digits! ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [October 3, 2004, 10:40am UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/33 "2004-10-03T10:40:55Z")
> [@Level3Navigator](#): > > For those who are into this, it is possible to calculate any digit of Pi (without having to calculate the previous digits) using the “BBP formula.” Take a look [here](http://crd.lbl.gov/~dhbailey/) . Truly an amazing and fascinating number. Hey, the BBP formula! I think one of those B’s is named for my old mailing-list pal, David H. Bailey, who I thought was just some random guy until I found out he was a famous mathematician. … and looking at the link, I see that it is indeed named for him, because that’s his site. ---
**Author:** ![Briny\_Deep](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/briny_deep/32/17188_2.png) [@Briny\_Deep](https://boards.straightdope.com/u/Briny_Deep)\ **Post date:** [October 3, 2004, 12:02pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/34 "2004-10-03T12:02:15Z")
Somebody’s got to mention, and apparently it must be me, “How I need a drink, alcoholic of course, after the heavy lectures involving quantum mechanics.” ---
**Author:** ![hammerbach](https://avatars.discourse-cdn.com/v4/letter/h/73ab20/32.png) [@hammerbach](https://boards.straightdope.com/u/hammerbach)\ **Post date:** [October 4, 2004, 5:38pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/35 "2004-10-04T17:38:00Z")
Blatant hijack: I know one for e (hope I get this right): “He repeats: I shouldn’t be tippling, I shouldn’t be toppling here…”. Any other irratinal constant mnemonics out there? ---
**Author:** ![Ms2001](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ms2001/32/18463_2.png) [@Ms2001](https://boards.straightdope.com/u/Ms2001)\ **Post date:** [October 4, 2004, 9:23pm UTC](https://boards.straightdope.com/t/a-few-questions-about-pi/266757/36 "2004-10-04T21:23:56Z")
Now I will a rhyme construct By chosen words the young instruct Cunningly devised endeavour Con it and remember ever Widths of circle here you see Sketched out in strange obscurity [Previous page](https://boards.straightdope.com/t/a-few-questions-about-pi/266757.md?page=1)