question which consists entirely of an image link, yikes: math.stackexchange.com/q/3481413/137524

(I'd call it a PSQ, but I'm not convinced it even reaches that threshold)

delete Not an answer

[ SmokeDetector | MS ] Potentially bad keyword in answer (1): Trouble integrating $\sec x$ by James Johnson on math.SE

D1, D2, D3.

D4, D5, D6.

D7, D8, D9.

D10, D11, D12.

D13, D14, D15.

C1, C2, C3.

C4, C5, C6.

C7, C8, C9.

C13, C14, C15.

→ 1 message moved to ­Trash

@user21820 Please don't delete D12. This is a very instructive problem that we don't have many other good examples for. I added some "work" but this is the sort of problem that if you don't know the key ideas you will be completely stuck.

@BillDubuque Alright.

@BillDubuque Makes complete sense. Can we agree that it ain't a great question, and should remain closed?

@user21820 I'm a little torn on D8; I'm not sure what additional context the asker could provide which would improve the question, and it seems like a reasonable question for the puzzle tag. On the other hand, it is a pretty bare question. My inclination is to leave it close, but not deleted. That being said, I don't have strong emotions in either direction.

@XanderHenderson I'm hoping someone with more time than I at the moment (e.g. the two contributors there) will add more, since it could be a good dupe target for contest questions like this. Also I think there could be other good answers too.

Alas, currently organization is very poor on topics related to "vieta jumping" or, more generally, on arithmetical aspects of [symmetries on conics[(math.stackexchange.com/a/1898116/242). It's on my TODO list, but not near the top at the moment. These topics deserve better exposure since they provide beautiful examples that help motivate more advanced number theory and algebra (a "poor man's" elliptic curve as Lemmermeyer says)

@BillDubuque My guess is that the asker is gone (the question is a year old, and the asker hasn't been "seen" since July). Perhaps the answerer could be prodded into making improvements?

That being said, my strategy with such questions has typically been to create a new question as a dupe target, and provide a CW answer of my own (I would mark the questions CW too, if I could, but the moderators have expressed a desire not to have a lot of CW questions running around).

I lack the expertise in this case, but perhaps someone more knowledgable could be asked?

@BillDubuque That is a very nice answer. Thank you.

Delete: DA, DB, DC, DD, DE, DF, DG