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: 
1. You have no way of knowing if the answer will truly be useless to the one asking the question.
2. "killing an ant with a nuclear bomb" So what? Is it a bad thing?
3. Answers are for everyone, not just the OP. Maybe these answers will be helpful to someone else. Considering that questions get closed for being duplicate of one another, if someone asks a question about some limit but displays high-school level knowledge, does it mean that everyone is forbidden from ever answering this limit using power series on this site?
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...?".