55: Useless

2014-07-03T21:22:25Z

173.245.51.212: /* Explanation */

{{comic
| number = 55
| date = January 27, 2006
| title = Useless
| image = useless.jpg
| titletext = Even the identity matrix doesn't work normally
}}

==Explanation==
[[Randall]] is attempting to apply mathematical systems 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 mathematical value, his normal approach is useless. Simply put: He's saying that math has no way of describing love (or more precisely, ''he'' has no way of describing love, using only the tools of mathematics.)

From the top, going right, he tries the {{w|square root}} of love; the {{w|cosine}} of love; the {{w|derivative}} of love with respect to x; he left-multiplies love by a 2x2 {{w|identity matrix}}, and finally he defines a {{w|Function (mathematics)|function}} of love as a {{w|Fourier transform}}. These may all be "normal approaches" to solving certain math problems.

The long and the short of the comic is that this might be the thinking of someone who uses math to solve all their problems upon their discovering love, which can't be solved with math.

===Basic explanations of the functions===
:''Note: The Wikipedia links will provide far more detailed explanations of the mathematics.''
*The square root of x is the number which, when multiplied by itself, equals x.
*Cosine is a {{w|trigonometric function}} which, 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).
*A 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.
*Identity matrices are matrices which 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.
*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==
:[Different mathematic equations, all with heart on left side, and all equal question mark. Equations are as follows:
:Square root of heart equals question mark
:Cosine of heart equals question mark
:Derivative of heart with respect to x equals question mark
:Identity matrix of heart equals question mark
:Fourier transform of heart equals question mark.]
:My normal approach is useless here

==Trivia==
*This is the fifty-second and last comic originally posted to LiveJournal. The previous comic was [[53: Hobby]].
*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 different one.
*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}}
[[Category:Comics posted on livejournal]]
[[Category:Romance]]
[[Category:Math]]

Talk:Title text

2014-07-03T20:55:57Z

173.245.51.212: Created page with "Everyone except this wiki calls it ‘alt-text’, Randall himself included. See XKCD 45. I vote for changing all occurrences of title text in this wiki to alt-text. --~~~~"

Everyone except this wiki calls it ‘alt-text’, Randall himself included. See XKCD 45. I vote for changing all occurrences of title text in this wiki to alt-text. --[[Special:Contributions/173.245.51.212|173.245.51.212]] 20:55, 3 July 2014 (UTC)

Talk:35: Sheep

2014-07-03T20:43:50Z

173.245.51.212: Created page with "It's Mareep attacking Cacnea! --~~~~"

It's Mareep attacking Cacnea! --[[Special:Contributions/173.245.51.212|173.245.51.212]] 20:43, 3 July 2014 (UTC)

explain xkcd - User contributions [en]

55: Useless

Talk:Title text

Talk:35: Sheep