# Phi number in THE DA VINCI CODE

**URL:** <https://boards.straightdope.com/t/phi-number-in-the-da-vinci-code/637608>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [October 13, 2012, 11:43am UTC](https://boards.straightdope.com/t/phi-number-in-the-da-vinci-code/637608 "2012-10-13T11:43:37Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![rf7627](https://avatars.discourse-cdn.com/v4/letter/r/858c86/32.png) [@rf7627](https://boards.straightdope.com/u/rf7627)\
**Post date:** [October 13, 2012, 11:43am UTC](https://boards.straightdope.com/t/phi-number-in-the-da-vinci-code/637608/1 "2012-10-13T11:43:37Z")

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Your article about the phi number in the da vinci code was awesome… I just want to tell you that when i tried it on various parts of my body, IT WORKED…it was amazing… :):):):)🙂  
THANK YOU 😉

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**Author:** ![C\_K\_Dexter\_Haven](https://avatars.discourse-cdn.com/v4/letter/c/b2d939/32.png) [@C\_K\_Dexter\_Haven](https://boards.straightdope.com/u/C_K_Dexter_Haven)\
**Post date:** [October 13, 2012, 12:14pm UTC](https://boards.straightdope.com/t/phi-number-in-the-da-vinci-code/637608/2 "2012-10-13T12:14:23Z")

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Welcome to the Straight Dope Message Boards, **rf7627** , we’re glad to have you with us.

For future ref, it’s helpful to other readers if you provide a link to the column when you start a thread. Saves search time and helps keep us all on the same page. In this case, I assume it’s: [Is phi a mystical number as claimed in The Da Vinci Code? - The Straight Dope](http://www.straightdope.com/columns/read/2513/is-phi-a-mystical-number-as-claimed-in-em-the-da-vinci-code-em)

No biggie, you’ll know for next time. And, as I say, welcome!

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**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\
**Post date:** [October 13, 2012, 9:23pm UTC](https://boards.straightdope.com/t/phi-number-in-the-da-vinci-code/637608/3 "2012-10-13T21:23:29Z")

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The exact value, by the way, is (1 + √5) / 2. (It only takes first-year algebra, but it’s too typographically messy to try to present it here.)

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**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\
**Post date:** [October 13, 2012, 10:16pm UTC](https://boards.straightdope.com/t/phi-number-in-the-da-vinci-code/637608/4 "2012-10-13T22:16:10Z")

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We have the definition ϕ[sup]2[/sup] = ϕ + 1, which is the same as saying (2ϕ - 1)[sup]2[/sup] = 5, as can be seen by distributing out (producing 4ϕ[sup]2[/sup] - 4ϕ + 1 = 5; i.e., 4ϕ[sup]2[/sup] = 4ϕ + 4; i.e., what we started with).

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**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\
**Post date:** [October 14, 2012, 7:02am UTC](https://boards.straightdope.com/t/phi-number-in-the-da-vinci-code/637608/5 "2012-10-14T07:02:51Z")

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One special property of the Golden Ratio is that, informally, it is the “most irrational” number. (Its continued-fraction representation is the worst-case, [1,1,1,1,1,1,1,…], meaning it has only poor rational approximants.)

This property is useful in [some heuristic scheduling algorithms](http://www.eng.tau.ac.il/~boaz/cd/Efficient%20Algorithms%20for%20Periodic%20Scheduling.pdf).