explain xkcd - User contributions [en]

Talk:1208: Footnote Labyrinths

2013-05-08T19:37:49Z

66.88.136.254:

Way to nerd-snipe me, Randall. [[User:Alpha|Alpha]] ([[User talk:Alpha|talk]]) 04:52, 6 May 2013 (UTC)

In the nested-footnotes interpretation, 5 has to be ignored: The 6 must be true, and the 6 says that it’s “actually a 1”, but with footnote 2+2 which says “ibid.” and thus equals footnote 3, which is true. So 6 really ''does mean'' actually a 1, which leaves 5 to be ignored. --[[Special:Contributions/77.186.8.191|77.186.8.191]] 10:47, 6 May 2013 (UTC)

The footnote for 6 is actually 1 to the 2 to the 2 [[User:Schmammel|Schmammel]] ([[User talk:Schmammel|talk]]) 12:36, 6 May 2013 (UTC)

Explaination is wrong : abc = a(bc) = ab^c (confer the definition of a gogol = 10^100 = 10102, and a gogolplex = 10^gogol = 10(10100), not 10^110. So since 1^2= 1, No12 really means No1. {{unsigned ip|192.54.145.66}}
:Yes, so "no1" means to ignore the "no" and the answer for the second explanation is "we found evidence for the data." By the way, it's spelled "googol." [[User:Alpha|Alpha]] ([[User talk:Alpha|talk]]) 17:51, 6 May 2013 (UTC)

;Question, alternative explination

I wasn't really satisfied with the whole discarding of the infinite loop, so I worked through the problem seperately using the nested footnotes. Then, when we hit the infinite loop I split between the two possible answers (either the infinite loop ends on true or false). As I read it, they both get the same answer:

no (3)

no (not true (5))

no (not true (true (2 < 6 < 3))

no (not true (true (2 < 6 < (not true))))

no (not true (true (2 < (actually 1 < 2 < 2 (not true 3 < 2)))))

no (not true (true (2 < (actually 1 < 2 < 2 (not true (5)))))

Split!

If 6 is false (infinite loop possibility)

no (3 < 5 < 2)

no (not true (7)) - meaningless, so discard

no (not true)

If 6 is true (infinite loop possibility)

no (3 < 5 < 1 < 2 < 2)

no (3 < 5 < 1 < 4)

no (3 < 5 < 1)

no (3)

no (not true)

Both lead to the answer "... experiments to observe this and we found evidence for it in our data". {{unsigned|‎Urah}}

:Yes, but at each stage you may "''toggle between interpreting nested footnotes as footnotes on footnotes and interpreting them as exponents (minus one, modulo 6, plus 1).''" That is, a23 may ''either'' be read as "apply note 8 (=2mod6) to text ''a''", or as "apply note 3 to text "2", then the result to text ''a''". {{unsigned ip|192.54.145.66}}
:There are differences in interpretation here. If we write "foo36", is it equal to "foo112" or "foo3112"? I assumed the former and you assumed the latter. My reasoning is that footnotes modify their arguments and not themselves. [[User:Alpha|Alpha]] ([[User talk:Alpha|talk]]) 17:44, 6 May 2013 (UTC)

Shouldn't 5 be true (because 6 is actually 13; therefore 5 is true2133; so the 2 is ignored regardless the truth of 3) and 3 is not true? Sebastian --[[Special:Contributions/178.26.118.249|178.26.118.249]] 18:35, 6 May 2013 (UTC)

'''Yet another alternative solution:''' Footnotes should be evaluated from top to bottom, so "no12" = "no1 + 2" = "no3". We turn to the definition of 3, which is "not true32" = "not true3 + 2" = "not true5".

Now 5 is "true263". The 6 says that the 2 footnote is really 122 = 1(4. ibid.) = 13, but the 3 tells us that the 6 is "not true5", getting us into an infinite loop. However, 263 must evaluate to 1, because otherwise we're incrementing "true" by 2, which is meaningless. This means that 3 must be equal "not true". 63 = "actually a 1"33 = "actually a 1". 5 becomes true1 which just says to ignore this footnote altogether and we can confirm that 3 is indeed not true (not true5 = not true). So the answer is that the "no" is not true, and the correct statement is "we found ''some'' evidence for it in our data." Phew. [[User:Ciamej|Ciamej]] ([[User talk:Ciamej|talk]]) 22:40, 6 May 2013 (UTC)

I'm not discouraging anyone from coming up with more alternate solutions, but would it be fair to say that part of the point is that there are multiple equally legit ways to run this labyrinth, and that some exit where you ignore the 'no', others exit on the other side where you don't ignore it. and then there's those who won't exit because they're busy making a map. - [[Special:Contributions/70.72.16.171|70.72.16.171]] 23:18, 6 May 2013 (UTC)

I don't understand the proof from ''This means that 3 = "true"''. Why do you assume that footnote has to be either "true" or "false? I think it could be "ignore this", "increment by three before following", "leave the whole calculation and assume we have two pieces of evidence" etc. as well. [[Special:Contributions/178.56.1.144|178.56.1.144]] 23:37, 6 May 2013 (UTC)
:Given the footnotes' definitions I don't think it's possible to ever come up with "increment by three before following" ;)
:Actually the solution I gave may be not strictly formal, but it gives some intuition why it seems to be the only valid one.
:The fact that the definitions are recursive doesn't imply that the ultimate answer cannot be resolved. [[User:Ciamej|Ciamej]] ([[User talk:Ciamej|talk]]) 02:18, 7 May 2013 (UTC)

So what I'm hearing is this, "No means No.", yes?[[Special:Contributions/66.88.136.254|66.88.136.254]] 19:37, 8 May 2013 (UTC)

Talk:1201: Integration by Parts

2013-04-24T19:32:48Z

66.88.136.254: Cheap humor

I think the joke is that's not the full explanation.
--[[Special:Contributions/128.113.151.84|128.113.151.84]] 04:30, 19 April 2013 (UTC)
: Exactly; he omits the final step part of the process: ∫udv= uv - ∫vdu. This is only helpful if you can easily obtain v from ∫dv and can integrate ∫vdu . The key trick is picking u and dv properly; it's rarely as easy as saying u = f(x) and v=g(x)dx. So the joke is that he's treating integration by parts as if it's a "magic rule" on the order of the product rule for differentiation, when it's not. [[Special:Contributions/66.202.132.250|66.202.132.250]] 21:10, 19 April 2013 (UTC)
:: I think this is it. It's funny because the described conversation happens universally every time someone who's not a full-blown math teacher tries to explain IBP to someone else. You just sort of hit this humiliating brick wall if you haven't comprehensively studied it. I'd also like to point out if u = v = x then dv = dx, f(x) = x, g(x) = 1 and your original integral was just ∫x dx to begin with (you wouldn't need IBP in the first place). [[User:Echo Seven|Echo Seven]] ([[User talk:Echo Seven|talk]]) 01:48, 21 April 2013 (UTC)

Not the full explanation?But what exactly is the joke here?It takes a lot of practice to be able to do integration sums correctly.[[User:Guru-45|Guru-45]] ([[User talk:Guru-45|talk]]) 05:26, 19 April 2013 (UTC)

I think the joke is rather “which definitely looks easier” — that’s how mathematics is generally perceived by non-mathematicians: You rewrite something, state that it looks easier / more beautiful / more elegant — which the non-mathematician usually perceives differently — and even if it does, you’re not a tad nearer to the answer. --[[Special:Contributions/84.191.162.248|84.191.162.248]] 08:00, 19 April 2013 (UTC)

Symbolic integration ALWAYS require experience and trial-and-error, which is flustrating given that the reverse process - derivation - can be described with simple alghorithm and done mechanically. I heart that derivation is easy as geting toothpaste out of tube and integration is reverse process ... meaning its as hard as puting the toothpaste back into tube. The reason is that there is simple rule for derivation of product, whereas integration of product is usually done by GUESSING the product which will derivate into given integral (which is what integration by parts actually is, only reformulated to sound little easier). -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 09:18, 19 April 2013 (UTC)

: By using the term ''derivation'', you mean it as the same as the term ''differentiation'', correct? I've never used the term derivation before. I like it, it's shorter. If so, YES, integration of products is WAY harder. 'u' substitutions alone are a pain - having a 'v' substitution as well requires a lot of hard work and trial and error... {{unsigned|Dangerkeith3000}}

''Oh, and add a '+C' or you'll get yelled at.''
Best part. This is something I experienced many times in my first semester of mathematics for scientists.
The joke seems to me to be the presentation of the idea accurately; after the initial step, there's no real advice to give. Good luck is the best you can hope for. [[Special:Contributions/49.176.36.57|49.176.36.57]] 12:37, 19 April 2013 (UTC)

Cripes, to do something by parts means to do something without enthusiasm or leave something incomplete. The joke is that he didn't complete the explanation! [[Special:Contributions/124.189.64.231|124.189.64.231]]

The title text refers to a ridiculously specific case (integrating x), which would not normally be done using integration by parts. This suggests that the narrator is pretending to know more about integration by parts than he actually does, which would explain why he left in such a hurry. [[User:Concomitant|Concomitant]] ([[User talk:Concomitant|talk]]) 11:43, 20 April 2013 (UTC)

: "''If you can manage to choose u and v such that u = v = x, then ...''"
It seems to me the problem here is in making such a choice. Suppose f(''x'') = ''x''^2, and g(''x'') = sin(''x''). How to split that?

Not only did he not complete the explanation -- he didn't really start it! All he did was describe how to convert from one of the *notation* systems for differential calculus, to the other. [[Special:Contributions/184.144.110.31|184.144.110.31]] 01:08, 22 April 2013 (UTC)

I think I would prefer the more sophmoric answer of (1/2)x^2 - C. After all the sum of the parts is greater than the whole, correct? [[Special:Contributions/66.88.136.254|66.88.136.254]] 19:32, 24 April 2013 (UTC)

Talk:1001: AAAAAA

2013-03-20T21:24:50Z

66.88.136.254: Turing beds anyone?

The usefulness of rotation in romance has been mentioned before in [[162: Angular Momentum]]. Perhaps the problem is that they are spinning the bed clockwise instead of counter-clockwise? [[User:Erenan|Erenan]] ([[User talk:Erenan|talk]]) 19:18, 28 August 2012 (UTC)

I think the difference lies in the commonly understood meaning of rotation as opposed to say spinning. Rotating can mean slow or fast, but spinning is usually faster. Is there a word that implies a gentleness to the rotation. They probably want a pivoting or turning bed. [[User:DruidDriver|DruidDriver]] ([[User talk:DruidDriver|talk]]) 01:00, 16 January 2013 (UTC)

Maybe Megan and Cueball would have been more turned on if they instead made a Turing bed.[[Special:Contributions/66.88.136.254|66.88.136.254]] 21:24, 20 March 2013 (UTC)

Talk:1061: EST

2013-03-13T20:01:23Z

66.88.136.254: a synopsis of a greater work, often with the intent to inform as quickly as possible.

"24 hours 4 minutes" because the period of rotation of the Earth is 24 hours MINUS four minutes.

EST = Eastern Standard Time (USA) or England Standard Time (UK); there's no easy way to disambiguate this since it is a common time zone for English speakers in the USA and UK.

"Run clocks backward" a possible reference to the leap second.

"0.9144" because 1 yard = 0.9144 meters

"triple 4 hours after every full moon" = add on an additional 12 hours every full moon, to make the time between full moons exactly 30 "days" (in real life it's 29.5 days). [[Special:Contributions/75.103.23.206|75.103.23.206]] 21:44, 7 December 2012 (UTC)

I seem to recall that Narnia time ran usually much faster but sometimes much slower than real-world time. [[Special:Contributions/130.160.145.224|130.160.145.224]] 20:51, 10 March 2013 (UTC)

I always thought that Taiwan, Province of China missed a golden opportunity here to establish propaganda that they founded it. Instead they are known as a township in the US. [[Special:Contributions/66.88.136.254|66.88.136.254]] 20:01, 13 March 2013 (UTC)

Talk:1073: Weekend

2013-03-12T20:10:58Z

66.88.136.254:

I usually start spewing this kind of nonsense when I lose track of what I'm saying in a speech. Who needs scripts? '''[[User:Davidy22|Davidy22]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 13:35, 8 January 2013 (UTC)

Since I am not well read regarding James Garfield's speeches perhaps this is an effort to point out that James Garfield's speeches were less compelling than the desire to avoid Monday's and how lasagna makes everything better.?[[Special:Contributions/66.88.136.254|66.88.136.254]] 20:10, 12 March 2013 (UTC)

Talk:1073: Weekend

2013-03-12T20:10:12Z

66.88.136.254:

I usually start spewing this kind of nonsense when I lose track of what I'm saying in a speech. Who needs scripts? '''[[User:Davidy22|Davidy22]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 13:35, 8 January 2013 (UTC)
Since I am not well read regarding James Garfield's speeches perhaps this is an effort to point out that James Garfield's speeches were less compelling than the desire to avoid Monday's and how lasagna makes everything better.?[[Special:Contributions/66.88.136.254|66.88.136.254]] 20:10, 12 March 2013 (UTC)