User kjo

10 votes

Prove that $\gcd(M, N)\cdot \mbox{lcm}(M, N) = M \cdot N$.

answered Jan 20, 2014 at 23:30

9 votes

Is every projection continuous?

answered May 8, 2013 at 3:24

7 votes

$X/{\sim}$ is Hausdorff if and only if $\sim$ is closed in $X \times X$

answered Jan 8, 2012 at 21:19

5 votes

Accepted

Error in book's definition of open sets in terms of neighborhoods?

answered May 28, 2013 at 12:50

5 votes

A Young Math Enthusiast's Fear

answered Jul 7, 2013 at 13:20

5 votes

Pedagogy: How to cure students of the "law of universal linearity"?

answered Jan 11, 2014 at 14:10

4 votes

Accepted

Why is Hardy motivating integrals be defining a new function $\phi'(x)=\psi(x)$?

answered May 7, 2013 at 22:00

3 votes

What's the dual of "inverse image" in Set?

answered Nov 9, 2011 at 13:48

3 votes

Looking for math audio resources online

answered May 6, 2012 at 16:07

3 votes

Accepted

Why is $H_1 \le G \land H_2 \le G$ necessary in $a(H_1 \cap H_2) = aH_1 \cap aH_2$?

answered Mar 14, 2014 at 10:02

3 votes

Gap in Halmos & Givant's "Logic as Algebra": undefined $\models$?

answered Jul 5, 2013 at 15:27

3 votes

Accepted

On the cardinality of a finite extension's Galois group

answered Mar 20, 2018 at 8:34

2 votes

Find the point on the y-axis which is equidistant from the points $(6, 2)$ and $ (2, 10)$.

answered Mar 16, 2014 at 19:31

2 votes

Accepted

Looking for proof that ($\mathbf{E} =$ coequalizers, $\mathbf{M} =$ monos) yields an image factorization system

answered Jan 28, 2012 at 5:25

1 vote

$(fg)(x)$ and $f(g(x))$. Commutability in Limits

answered Jan 29, 2012 at 11:37

1 vote

Looking for proof of monicity of co-product insertions

answered Jul 30, 2011 at 4:52

1 vote

General request for a book on mathematical history, for a VERY advanced reader.

answered May 19, 2018 at 16:20

1 vote

Unexpected tangency

answered Aug 30, 2023 at 0:48

1 vote

Simple proof that symmetries of regular polyhedron fix its center?

answered Jan 1, 2014 at 19:14

1 vote

Accepted

How to convert the ln part of this equation to log10?

answered Mar 14, 2014 at 11:01

1 vote

How to prove $\frac{1}{q} \binom{p^k q}{p^k} \equiv 1 \mod p\;\;$?

answered Jan 30, 2014 at 12:34

0 votes

Expectation expression

answered Mar 14, 2014 at 16:27

0 votes

Prove that an infinite sequence of nested closed intervals contains a point common to all intervals.

answered May 7, 2013 at 19:05

0 votes

What are the prerequisites to Jech's Set theory text?

answered Mar 20, 2022 at 14:41

0 votes

Carmichael proof of at least 3 prime factors

answered Jun 30, 2013 at 13:55

0 votes

Accepted

On the period of the decimal representation of $n$ when $\gcd(n, 10) \neq 1$

answered Jun 29, 2013 at 20:35

0 votes

Is the identiy function continous on equivalent metric spaces

answered Jul 6, 2013 at 23:02

0 votes

Accepted

Construction of a partial order on a quotient of a coproduct

answered Feb 21, 2012 at 2:02

0 votes

On permutations of left cosets

answered Dec 26, 2011 at 14:20

-1 votes

Accepted

Are the lengths from this recursive construction a geometric sequence?

answered Apr 16, 2013 at 11:25

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30 Answers

Prove that $\gcd(M, N)\cdot \mbox{lcm}(M, N) = M \cdot N$.

Is every projection continuous?

$X/{\sim}$ is Hausdorff if and only if $\sim$ is closed in $X \times X$

Error in book's definition of open sets in terms of neighborhoods?

A Young Math Enthusiast's Fear

Pedagogy: How to cure students of the "law of universal linearity"?

Why is Hardy motivating integrals be defining a new function $\phi'(x)=\psi(x)$?

What's the dual of "inverse image" in Set?

Looking for math audio resources online

Why is $H_1 \le G \land H_2 \le G$ necessary in $a(H_1 \cap H_2) = aH_1 \cap aH_2$?

Gap in Halmos & Givant's "Logic as Algebra": undefined $\models$?

On the cardinality of a finite extension's Galois group

Find the point on the y-axis which is equidistant from the points $(6, 2)$ and $ (2, 10)$.

Looking for proof that ($\mathbf{E} =$ coequalizers, $\mathbf{M} =$ monos) yields an image factorization system

$(fg)(x)$ and $f(g(x))$. Commutability in Limits

Looking for proof of monicity of co-product insertions

General request for a book on mathematical history, for a VERY advanced reader.

Unexpected tangency

Simple proof that symmetries of regular polyhedron fix its center?

How to convert the ln part of this equation to log10?

How to prove $\frac{1}{q} \binom{p^k q}{p^k} \equiv 1 \mod p\;\;$?

Expectation expression

Prove that an infinite sequence of nested closed intervals contains a point common to all intervals.

What are the prerequisites to Jech's Set theory text?

Carmichael proof of at least 3 prime factors

On the period of the decimal representation of $n$ when $\gcd(n, 10) \neq 1$

Is the identiy function continous on equivalent metric spaces

Construction of a partial order on a quotient of a coproduct

On permutations of left cosets

Are the lengths from this recursive construction a geometric sequence?