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| date = January 27, 2006
 
| date = January 27, 2006
 
| title = Useless
 
| title = Useless
| before    = <big><big><span class="plainlinks">[https://web.archive.org/web/20060529063441/http://xkcd-drawings.livejournal.com/#:~:text=4%3A38%20am-,Useless,-(3%20Comments LiveJournal title</span>]: '''Useless'''</big></big>
 
 
| image = useless.jpg
 
| image = useless.jpg
 
| titletext = Even the identity matrix doesn't work normally
 
| titletext = Even the identity matrix doesn't work normally
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==Explanation==
 
==Explanation==
This was the fifty-second and last comic originally posted to [[LiveJournal]]. The previous one was [[53: Hobby]], but the next comic, [[56: The Cure]], was never posted to LiveJournal. It was among the [[:Category:Posted on LiveJournal after xkcd.com|last eleven comics]] posted both on LiveJournal and on [https://xkcd.com xkcd.com] after the new site was launched. This comic was published on the same day across both sites, but not all of them shared the same posting day.
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[[Randall]] is attempting to apply mathematics to the concept of love to no avail. Specifically, he is attempting his "normal approach", which is a term used in mathematics for the method one typically uses to solve a certain type of problem. However, as love is not a well-defined mathematical entity, his normal approach is useless. Simply put: he's saying he has found no way of describing love using only the tools of mathematics.
  
[[Randall Munroe|Randall]] is attempting to apply mathematics to the concept of love to no avail. Specifically, he is attempting his "normal approach", which is a term used in mathematics for the method one typically uses to solve a certain type of problem. However, as love is not a well-defined mathematical entity, his normal approach is useless. Simply put: he's saying he has found no way of describing love using only the tools of mathematics.
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From the top, moving left to right, he tries the {{w|square root}} of love, the {{w|cosine}} of love, and the {{w|derivative}} of love with respect to x. He then attempts to left-multiply love by a 2x2 {{w|identity matrix}}, and finally he defines a {{w|Function (mathematics)|function}} of love as a {{w|Fourier transform}}. These are all "normal approaches" to solving certain math problems.
  
From the top, moving left to right, he tries the {{w|square root}} of love, the {{w|cosine}} of love, and the {{w|derivative}} of love with respect to x. He then attempts to left-multiply love by a 2x2 {{w|identity matrix}}, and finally he defines a {{w|Function (mathematics)|function}} of love as a {{w|Fourier transform}}. These are all "normal approaches" to solving certain math problems. The message of the comic is that for someone who uses math to solve all their problems, defining love is impossible.  It also indicates that love is not always a rational (or irrational) phenomenon.
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The message of the comic is that for someone who uses math to solve all their problems, defining love is impossible.  It also indicates that love is not always a rational (or irrational) phenomenon.
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This comic has been made into a [http://store.xkcd.com/products/useless t-shirt] in the xkcd store, with a {{w|Laplace transform}} in place of the bottom integral.
  
 
===Basic explanations of the functions===
 
===Basic explanations of the functions===
* The {{w|square root}}s of x are the two numbers (positive and negative) where each multiplied by itself equals x. Often only the positive answer is quoted.
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:''Note: The Wikipedia links will provide far more detailed explanations of the mathematics.''
* {{w|Cosine}} is a {{w|trigonometric function}} that, when given the measure of an angle in a {{w|right triangle}} as an input, outputs the ratio of the lengths of two sides of that triangle (for cosine, it is the non-{{w|hypotenuse}} side adjacent to the angle and the hypotenuse).
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*The {{w|square root}} of x is the number that, when multiplied by itself, equals x.
* A {{w|derivative}} of a function is the rate of change of that function at a given value of x. It is a primary focus of {{w|calculus}}. A basic example is where "velocity" is the rate of change of displacement at a given time, the derivative of velocity is "acceleration", which is the rate of change of velocity at a given time.  
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*{{w|Cosine}} is a {{w|trigonometric function}} that, when given the measure of an angle in a {{w|right triangle}} as an input, outputs the ratio of the lengths of two sides of that triangle (for cosine, it is the non-{{w|hypotenuse}} side adjacent to the angle and the hypotenuse).
* {{w|identity matrix|Identity matrices}} are {{w|matrix (mathematics)|matrices}} that consist of only zeros and ones, with zeros everywhere except along the {{w|main diagonal}}. Multiplying a matrix by the equal-sized identity matrix will result in the same output in the same way that multiplying a non-matrix by 1 does not change the original term. The title text suggests that multiplying love by the identity matrix does not return the same "love" value.
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*A {{w|derivative}} of a function is the rate of change of that function at a given value of x. It is a primary focus of {{w|calculus}}. A basic example is where "velocity" is the rate of change of displacement at a given time, the derivative of velocity is "acceleration", which is the rate of change of velocity at a given time.  
* A {{w|Fourier transform}} converts a function from one (sophisticated) function into an endless continuous series of simpler functions, where each next part is bringing the equation closer to the real result. This means that you can stop your calculations after a few iterations and you are very close to the real result, and it also can be used to deconstruct signals.
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*{{w|identity matrix|Identity matrices}} are {{w|matrix (mathematics)|matrices}} that consist of only zeros and ones, with zeros everywhere except along the {{w|main diagonal}}. Multiplying a matrix by the equal-sized identity matrix will result in the same output in the same way that multiplying a non-matrix by 1 does not change the original term. The title text suggests that multiplying love by the identity matrix does not return the same "love" value.
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*A {{w|Fourier transform}} converts a function from one (sophisticated) function into an endless continuous series of (more simple) functions, where each next part is bringing the equation closer to the real result. This means that you can stop your calculations after a few iterations and you are very close to the real result, and it also can be used to deconstruct signals.
  
 
==Transcript==
 
==Transcript==
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:<sup>[0 1]</sup>
 
:<sup>[0 1]</sup>
 
:F{♥} = 1/√2π ∫<sup>∞</sup><sub>-∞</sub>f(t)e<sup>it♥</sup>dt = ?
 
:F{♥} = 1/√2π ∫<sup>∞</sup><sub>-∞</sub>f(t)e<sup>it♥</sup>dt = ?
:[Caption below the equations:]
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:[Caption below:]
 
:My normal approach is useless here.
 
:My normal approach is useless here.
  
 
==Trivia==
 
==Trivia==
* In the book ''[[xkcd: volume 0]]'', this comic is slightly different. The derivative is with respect to time (''t'') instead of ''x'', and the function at the bottom is a {{w|Laplace transform}} instead of the bottom integral.
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*This was the 52nd and last comic originally posted to [[LiveJournal]].
* Also in the book, a cipher is displayed prominently below the comic:
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**The previous was [[53: Hobby]].
 
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**The next comic [[56: The Cure]] was not also posted on LiveJournal
<pre>
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***This thus ends this repeating trivia section that has been present for all those 52 LiveJournal comics.
CY-O CMLROOCXN. YR M.AOGP. NRK.W ABE ,CYDRGY M.AOGP.M.BY YD.P. JAB X. BR OJC.BJ.V <D.B CY JRM.O YR NRK.W ,.-P. ANN CB YD. EAPTV [[TCBO.F
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***Also after this there has been no issue with comics released at two times, since they were now released only on xkcd.
</pre>
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*This comic kept its original title: "Useless"
 
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**It is part of the last six comics on LiveJournal which all had a title without the word "Drawing" in it.  
:This is a Dvorak to Qwerty cipher. Undeciphered, it reads:
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**Five of these had exactly the same title on both sites.
 
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**Only 11 comics have the same title on both sites.
::it"s impossiblE to mEasurE lovE, and Without mEasurEmEnt thErE can bE no sciEncE. whEn it comEs to lovE, WE"rE all in thE dark. __kinsEy
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**Apart from the [[:Category:First day on LiveJournal|thirteen first comics]] posted to LiveJournal, there were only three other comics without the word "Drawing" in the title before these last six.
::: It's impossible to measure love, and without measurement there can be no science. When it comes to love, we're all in the dark. --{{w|Kinsey_(movie)|Kinsey}}
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*There was no original [[Randall]] quote for this comic.
<!--(Although it is worth noting that this was never said verbatim, Alfred Kinsey is quoted as saying this.)
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*This comic was the last of the last 11 comics posted on LiveJournal.
The quote in question: [https://en.wikiquote.org/wiki/Kinsey_(film)]-->
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**These 11 comics were [[:Category:Posted on LiveJournal after xkcd|posted both on LiveJournal and xkcd]] after the [[xkcd]] site opened on the 1st of January 2006.
* The modified book version used to be [https://web.archive.org/web/20211215085605/https://store.xkcd.com/products/useless available as a T-shirt] in the xkcd store before it was [[Store|shut down]].
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**The first six comics were posted on both sites on the same day.  
* This used to be one of the [[Footer comics|footer comics]] featured in the bottom segment of [https://xkcd.com xkcd.com].
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**And then this first happened again with this last comic.
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*The version used on the [http://store.xkcd.com/products/useless t-shirt] and in ''[http://store.xkcd.com/products/xkcd-volume-0 xkcd: volume 0]'' is slightly different. The derivative is with respect to time (''t'') instead of ''x'', and the function at the bottom is a {{w|Laplace transform}}.
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*This comic was adapted to a wedding cake featured on [http://www.cakewrecks.com/home/2011/6/26/sunday-sweets-geek-wedding-cakes.html an installment of  "Sunday Sweets"], a regular feature on popular blog [http://cakewrecks.com Cake Wrecks].
  
 
{{comic discussion}}
 
{{comic discussion}}
  
[[Category:Posted on LiveJournal| 52]]
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[[Category:Comics posted on livejournal| 52]]
[[Category:Posted on LiveJournal after xkcd.com]]
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[[Category:Posted on LiveJournal after xkcd]]
 
[[Category:Romance]]
 
[[Category:Romance]]
 
[[Category:Math]]
 
[[Category:Math]]

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