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2:39 PM
This user asks for help with searching for a duplicate, perhaps somebody can help them:
Although I'm a bit agnostic about the value of creating a handful of such tags (not opposed, but they seem in many cases useful only to those who already know to ask for them "by name"), I happened to pop in here looking for an abstract duplicate for the canonical application of the intermediate value theorem. — hardmath 1 min ago
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Q: Suppose f and g are continuous on [a, b] and that f(a) < g(a), but f(b) > g(b). Prove that f(x) = g(x) for some x in [a, b].

liveFreeOrĪ€HardI have been asked to prove the following question for my Real Analysis course, and I'm not quite sure how to go about proving this. The textbook is Spivak's Calculus, and this is question 10 from Chapter 7. Thank you in advance! Suppose $f,g$ are continuous on $[a, b]$ and that $f(a) < g(a)$, bu...

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Q: Proving that $f(x) = g(x)$ for some $x \in [a,b]$ if $f,g$ continuous, $f(a) < g(a)$ and $f(b) > g(b)$

John Snow Suppose $f$ and $g$ are continuous on $[a,b]$ and that $f(a) < g(a)$ but $f(b) > g(b)$. Prove that $f(x) = g(x)$ for some $x \in [a,b]$.

@hardmath This seems to be unrelated to the question here. (Or only very weakly related.) So I would suggest that if you wish to discuss searching for duplicates, the discussion should ideally be moved to chat. — Martin Sleziak 9 secs ago
I will also that there is also another chat room where you might find help with searching for questions: In the search of a question.
I posted here, since the topic of this room is closer to discussing duplicates.
The above was what I found by a quick Google search, but there are probably many other copies of that question.
There's some linkage between tags and abstract duplicates in that our list of common Questions is organized by tags. IVT fits somewhere between precalculus and calculus perhaps, but isn't found there (yet). — hardmath 1 min ago
This one is also close:
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Q: If $f$ and $g$ are continuous on $[a,b]$, $f(a) \le g(a)$, and $g(b) \le f(b)$, prove there is a c in [a,b] with $f(c)$ $=$ $g(c)$.

CarlIf $f$ and $g$ are continuous on $[a,b]$, $f(a)$ $\le$ $g(a)$, and $g(b)$ $\le$ $f(b)$, prove there is a point $c$ $\in [a,b]$ such that $f(c)$ $=$ $g(c)$. Any ideas on how to solve? I think I have to use the Intermediate Value Thm but I'm not sure.

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Q: Prove $f(x)=g(x)$ has at least 1 solution $c$ in $(a,b)$

sarahIf $f$ and $g$ are two continuous functions from $[a,b]$ to real numbers s.t $f(a)\lt g(a)$ and $f(b)\gt g(b)$. Prove that $f(x)=g(x)$ has at least 1 solution $c$ in $(a,b)$. I tried using intermediate value theorem. It states that if f continuous on [a,b] f(a)< d< f(b) then there exists a point...

3
Q: Prove if $f(a)<g(a)$ and $f(b)>g(b)$, then there exists $c$ such that $g(c)=f(c)$.

RedFirst of all, let me write the statement properly: Theorem : Let $f(x)$ and $g(x)$ are continuous on a closed interval $[a,b]$. If $f(a)< g(a)$ and $f(b)>g(b)$, then there exists a $c$ in the interval $[a,b]$ such that $f(c)=g(c)$. I am new at proofs, so I wanted ask if the proof below c...

3
Q: Prove that there is $c \in [a,b]$ such that $f(c) = g(c)$

Puzzled417 Suppose $f,g: [a,b] \to \mathbb{R}$ are continuous such that $f(a) < g(a)$ and $f(b) > g(b)$. Prove that there is $c \in [a,b]$ such that $f(c) = g(c).$ Attempt: Let $h(x) = f(x) - g(x)$. Then $h(a) < 0$ and $h(b) > 0$ while there exists a $c$ such that $h(c) = 0$. Then isn't it obvious tha...

Although the last one seems to be question.
 
@Martin: I removed my original Comment from your Question on Meta, but my point is that tags are for searching, and searching for duplicates is especially important. I think it is fair to say you are finding duplicates, which means that it could be helpful to include this in the list of Common Questions. But to an extent we have difficulty in pigeonholing it there for lack of a tag.
 
Since we were able to find several copies very quickly, it seems very probable that there are many of them.
@hardmath I definitely did not want to bully you into removing the comment if you thought it was relevant. But your comment seemed to me more like "Help me find duplicates of this." From this viewpoint it seemed to be very far from what that question is about.
@hardmath So basically you are saying that would be useful, because there are many questions using Intermediate value theorem and this would make finding them easier?
I am not sure to which extent searching using tags would - in this specific case - be much different from searching for the name of theorem.
 
2:56 PM
Chat is good ! The Question I was dealing with came up in the Reopen review, so I was going to vote not to reopen but leave a Comment linking to the abstract duplicate. Not finding it leads me toward the value of having tags for named theorems, at least at the introductory calculus/analysis level.
 
Well, if you think that separate tags for some calculus theorems would be useful, maybe you should post an answer and explain your arguments.
My opinion is different, and past discussions about Squeeze theorem and Mean value theorem linked in my meta post seems to indicate that the community as a whole is not very keen on such tags. But it is possible that you will be able to get some support for such tags on meta.
I will just point out that simply having the tag will probably not help with searching for duplicates, at least no immediately - you also need that people start actually using the tag. So if the tag gains some support and is created, there is still a lot of work to do - at least the most frequent questions related to that tag should be retagged.
Probably at least some of the above question should be closed as duplicates.
 
3:37 PM
Thanks for adding the Comment on the original "duplicate" that I mentioned, and I will make a list of the one you've found and vote to close as duplicate (all but one!).
 
Ok. Thanks for taking your time to look into those question.
I'll copy here this:
"I think finding duplicates and closing questions as duplicates is useful. If caught early, this prevents answerers from redoing the work which has already been done. But even after answering, closing duplicates helps to concentrate the relevant information in one place rather than scattered in various post. And it also directs the users who found one of several copies of the same question to the copy which has the best answers."
 

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