This has been bugging me lately. A very large amount of questions ask for proofs of certain facts which are 100% definition dependent.

Since we've made a huge progress with homework as to include some of what many people agree is a good homework policy, would it be sensible to include a

Don't forget to include the definitions you're using if they are relevant to your question! As a an example, see this, this this, and this. And this.


  • $\begingroup$ Yes! Explain all notation you are using. $\endgroup$ – Andrés E. Caicedo Sep 15 '13 at 1:58
  • $\begingroup$ @AndresCaicedo ? $\endgroup$ – Pedro Tamaroff Sep 15 '13 at 1:59
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    $\begingroup$ I agree with you, Peter. The disclaimer should ask people to "explain all ..." $\endgroup$ – Andrés E. Caicedo Sep 15 '13 at 2:08
  • $\begingroup$ @AndresCaicedo Heh. For a moment I thought you were being sarcastic. $\endgroup$ – Pedro Tamaroff Sep 15 '13 at 2:10
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    $\begingroup$ Ideally, yes. I've seen so many questions, where the asker apparently believes that the definition/notation in their textbook is in universal use. Early in their careers people simply have not been exposed to enough many texts - well we all started from a single book! I think we could include a warning in the FAQ about this, but expecting people to comply and understand the reason for this is asking a lot. $\endgroup$ – Jyrki Lahtonen Sep 15 '13 at 6:04
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    $\begingroup$ @JyrkiLahtonen That did cross my mind. Maybe one can see it as a chance for people to learn new things at the same moment. Someone might be kind enough to make an article. "Why do definitions matter?". I don't think I am the appropriate candidate! =P $\endgroup$ – Pedro Tamaroff Sep 15 '13 at 6:05
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    $\begingroup$ @Jyrki: We can always include a clause allowing us to legally fire them in case they disregard this point. And of course, when I say fire, I mean out of a cannon. Into the sun. $\endgroup$ – Asaf Karagila Sep 15 '13 at 11:09
  • $\begingroup$ @AsafKaragila: Although Jules Verne considered such a means of travel, it has serious practical difficulties. Even if, as in this case, fatally high acceleration is not a problem, atmospheric drag and gravity are huge ones. The muzzle velocity of the cannon will have to be substantially greater than escape velocity. Even if you could pack that much punch into a cannon, I doubt very much that the craft would remain intact for long. $\endgroup$ – dfeuer Sep 16 '13 at 7:31
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    $\begingroup$ This question needs more upvotes. As Jyrki Lahtonen pointed out, the asker apparently believes that the definition/notation in their textbook is in universal use. $\endgroup$ – Git Gud Sep 18 '13 at 16:35
  • $\begingroup$ maybe also question to include booktitles where appropriate $\endgroup$ – Willemien Oct 4 '13 at 18:58
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    $\begingroup$ @dfeuer: You obviously missed the clear reference to Futurama; more specifically the very first episode. $\endgroup$ – Asaf Karagila Oct 5 '13 at 0:34
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    $\begingroup$ Also: We should not be shy about putting questions on hold until definitions (etc.) are inserted by the OP. $\endgroup$ – GEdgar Nov 4 '13 at 15:10

I use to be a little bit lazy with including definitions/theorems from my book. I know use a method that makes pasting definitions realy easily done using adobe reader and http://snag.gy/:

  1. Adobe Reader -> Edit -> Take a snapshot
  2. Select the text you want to copy
  3. Crt-V at http://snag.gy/

And the rest should speak for itself. For example:



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