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"We encourage children to read for enjoyment, yet we never encourage them to 'math' for enjoyment. We teach kids that math is done fast, done only one way and if you don't get the answer right, there's something wrong with you. You would never teach reading this way." - Rachel McAnallen

"Mathematicians create by acts of insight and intuition. Logic then sanctions the conquests of intuition." - Morris Kline


6h
asked Where can I find linear algebra described in a pointfree manner?
11h
comment What is a conventional name for a set of values having no properties except that values are distinct?
onlyidentity is right, see here. This distinction really ought to be more widely appreciated.
11h
comment Is zero an even number?
@azimut, I've already done it man. We can probs ask a question on meta asking for a final downvote hahaha :)
13h
answered Why we throw away the units in the definition of irreducible elements?
1d
asked What abstract structures allows us to describe “nets that converge toward each other”?
1d
comment Infinity in “Extended Natural Numbers”
I don't know the answer, but you should look into net convergence, and think about nets $\omega+1 \rightarrow X$ where $X$ is a topological space, and $\omega+1$ is the successor of $\omega$, where $\omega = \{0,1,2,3,\ldots\}$ is the least infinite ordinal numbers.
1d
comment An easy example of a non-constructive proof without an obvious “fix”?
But surely, Neil, this is still a theorem even if the ambient logic is intuitionistic?
1d
answered What is a conventional name for a set of values having no properties except that values are distinct?
1d
comment How can we think and/or write rigorously about integration by substitution?
@GitGud, thanks, that is a very useful comment.
1d
accepted How can we think and/or write rigorously about integration by substitution?
2d
awarded  Nice Question
2d
comment How can we think and/or write rigorously about integration by substitution?
@k.stm, thanks for the tip.
2d
revised How can we think and/or write rigorously about integration by substitution?
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2d
revised How can we think and/or write rigorously about integration by substitution?
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revised How can we think and/or write rigorously about integration by substitution?
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2d
asked How can we think and/or write rigorously about integration by substitution?
2d
comment Greatest common factor in a category
@HenningMakholm, glad I was able to help you for a change :)
Jan
24
comment Greatest common factor in a category
Okay, I've posted my understanding of the construction. Perhaps something better will come along though. I would Google "colimits in slice categories" in the search for further information.
Jan
24
answered Greatest common factor in a category
Jan
24
comment Greatest common factor in a category
Yep, I think I get you. Given a pair of arrows $f,g : A,B \rightarrow \Omega$ with common codomain, I think you're interested in the coproduct of $f$ and $g$ viewed as objects of the slice category of $\Omega$. When $f$ and $g$ are injective functions, this is the "union" of $A$ and $B$.