Question: I've seen a lot of questions of rather elementary limits (most of them 'highschool' level), where users answer saying things like

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> "Note that $\sin x =\sum \frac {(-1)^n}{(2n+1)!}x^{2n+1}$, then it's rather trivial $\dots$"
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Or

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> "Just remember that $\sqrt x \in o(x)$, then $\dots$"
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I'm always disappointed at seeing answers like that, it's utterly obvious they'll be useless for the one asking the question (and most of the times it's really kind of "killing an ant with a nuclear bomb").

What do you guys think?

Answer: 
I think such answers should not be downvoted merely because they are beyond the presumed understanding of the OP. (There may of course be other reasons to downvote the answer.) In the first place, "answers are for everyone." I can't count the number of times that I've learned something here because someone else introduced a more powerful technique than I was aware of. (Well, obviously it's *countable*, but—oh, you know what I mean.) In the second place, who can say for sure what the OP knows, or can apprehend once shown?

As for frowning upon such answers—to be sure, no one can know if you frown upon something, but in my opinion, it's not productive to censure someone (not censor) for using a sledgehammer instead of a flyswatter. My countersuggestions:

* Let the OP comment on the answer if they don't find it helpful; their feedback is more likely to elicit a positive response from the answerer than someone from the peanut gallery.
* Upvote the answers you *do* approve of, rather than downvote the one you don't.
* If no one else has provided a more elementary solution, it may behoove you to add one.
It is not necessary that answers are useful to the author. Nice side effect when it happens, but it is not a reasonable expectation to impose on the question/answer dialogue. 

Fortunately, almost any correct answer that is not an extreme digression from the point could be useful. If a simple limit question gets answers using power series, that can be a hint to anyone interested to learn about power series, and a valuable connection to remember whenever the learning about power series happens. "These things can be used to compute limits! Where did I see that before...?".