EDIT: Could the downvoter please let me know if I should improve my question in some way. For clarity, I am asking whether what I describe below is considered plagarism, and if so what the approporiate course of action to take is.

I am very concerned about an assignment I submitted recently for mathematics, and that I may be accused of plagarism. The assignment consisted of several questions. For a part of one of these, I had come across something similar in a slightly different context in a talk I had given a couple of weeks earlier. It was just an aside around the reading I was doing- it was actually a named theorem, but at the time I didn't register it, but I remembered gathered the sketch of the proof and moved on. With this proof, it is of the form that when you frame the problem in the right way, then the proof just flows and it isn't really possible to modify it in any way. It also seems fairly general- I didn't read it in a paper, it must have been on some general expository website on topics relating to my area of math or a blog post.

So I used this framework for my problem (I iterate was in a different context) and wrote up the proof. At the time, I had a small thought as to whether I should try to track down a source similar to whatever it was that I had come across in preparing the talk. For some reason I decided that it was unecessary because it was just a framing of the problem that I started arriving at myself (which is why I recognised the connection to this different context) and secondly because, as noted above, it seemed like something fairly standard that one might come across in a course on the topic.

But now I am panicking for two reasons. Firstly, I feel that I have not given proper credit to the person who came up with this framing of the problem and proof in a different context (even if it is standard now, it was not once in the past). Secondly, as mentioned above it is essentially impossible to modify the proof once you have the framing, so what I wrote looks very similar to other sources. Heck, now that I've been panic checking for this theorem online, I've found pages\lecture notes which actually use almost exactly the same notation as me because the choice of notation is very natural.

I feel sick to my stomach, and feel compelled to write to someone to say that the idea for the proof was from elsewhere, but I do not know if this will help the situation. I was very tired and writing up the assignment in a bit of a rush before the deadline, so I was less vigilant about referencing than I should have been. As an aspiring academic, I am absolutely disgusted with myself that I did not give proper credit to whoever came up with this proof first just because it felt 'standard' and 'assumable', like the kind of toolbox set of techniques one picks up in a course.

Whatever the official outcome will be, I have learnt my lesson simply because of the anxiety and worry I feel now. But I would appreciate some advice on this. I'm finding it hard to judge myself if what I did was wrong or not, because this is mathematics. What distinguished 'copying a proof' from 'having read the proof at some point in the past and acquired the gist as a useful technique that I am now applying'? I am quite confused.

  • Are you an undergraduate? If so, which year of study? Commented Jan 15, 2021 at 17:08
  • @astronat Masters, so I should know better. I have never had assignments of this form before though, and during undergrad I had only written exams and a couple of expository essays to write, where I somehow never had a dilemma of what I could consider 'assumable knowledge'. I'm still conflicted in the present case.
    – JaimePQ
    Commented Jan 15, 2021 at 17:21
  • 1
    Was this question a "research" question? Were you asked to research it and present a solution based on research?
    – Buffy
    Commented Jan 15, 2021 at 19:04
  • @Buffy Not really a research question. It more resembled a difficult exercise sheet one might get at the the end of a course, with some of the questions a bit more open ended e.g. 'what's the best bound you can find...'. This one was not. It was simple a 'prove that...'.
    – JaimePQ
    Commented Jan 15, 2021 at 19:06
  • 4
    I didn’t downvote, but my guess would be that someone didn’t like that an issue that could be completely described in one paragraph was presented in an unnecessary step-by-step fashion (it seems to be something like: “For a hw assignment that I solved relying on a proof I had read in the past online, I ended up writing a solution that could come across as having copied part of that old proof. Is this plagiarism? Should I bring it up with my teacher?”). Commented Jan 15, 2021 at 19:28

2 Answers 2


Contact the professor now, if for no other reason than to get out of your panic spiral.

Let them know that you are concerned that you failed to appropriately cite your sources and that you are generally confused about what can be treated as assumed knowledge and when you should credit a source.

You could even go as far as submitting a version of your assignment that does cite sources more completely.

This can be a learning experience. Go ahead and be an active part of that process.

  • Thanks very much for the advice! Will upvote when I have the rep.
    – JaimePQ
    Commented Jan 15, 2021 at 22:59

As long as the question wasn't specifically intended as a research question, but rather an exam question or ordinary assignment, I wouldn't be concerned if I were your professor.

You were given an assignment and in a limited time frame remembered something you'd been told earlier, that wasn't exactly the answer, but allowed you to reconstruct the answer to the question. I don't see any issue with that in this context.

If you were to develop this into a paper, given a longer time scale, then you would be expected to trace down some such things, provided that they aren't already common knowledge (to professionals if not to students).

I doubt that any issue will be raised, but if it is, just explain yourself as you have here. The "kernel" of most of the things you now know were told to you at one time or another. You don't need to start every answer with "A professor once mentioned..."

There is nothing wrong with the answer of Dancrumb but I doubt that it is necessary to contact the professor. This just doesn't have the feel of someone trying to behave dishonestly or even carelessly.

  • I whole-heartedly agree that it's probably not necessary to contact the professor and it will probably come to nothing. Hopefully, your answer will help the OP feel calmer and they can follow up with questions about how and when to cite sources (or not) in a more relaxed manner.
    – Dancrumb
    Commented Jan 15, 2021 at 20:29
  • Thank you very much Buffy! Fingers crossed it will be ok. Will upvote when I have the rep
    – JaimePQ
    Commented Jan 15, 2021 at 23:02

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