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Apr
15
comment Determine if $g$ is a ring homomorphism
Write down the formula that must hold for $g$ to commute with multiplication and then look for a counterexample.
Apr
15
answered Listing all the ideals of a quotient ring
Apr
14
answered Jordan Canonical form 3x3
Apr
14
comment Jordan Canonical form 3x3
The characteristic polynomial of a 3x3 matrix should have degree 3, you've written down something that has degree 4.
Feb
28
awarded  Enlightened
Jan
10
awarded  Yearling
Dec
14
awarded  Nice Answer
Nov
22
comment Triangulation of the Klein Bottle
I disagree, but we may be talking about two different things. When he says edge 12 is shared by 4 triangles I think that means he's identifying all four edges of the square. I'm only identifying the top/bottom edges with themselves and the left/right edges with themselves. I see now this isn't explicit in the OP's picture, but it makes the answer correct and it's what I assume he meant.
Sep
24
answered If $G$ is a group with $|G|=2m$ and $m$ odd, then $G$ has exactly one element of order two
Sep
8
revised Semidirect product structure of Dihedral group
added 83 characters in body
Sep
8
revised Semidirect product structure of Dihedral group
added 83 characters in body
Sep
8
answered Semidirect product structure of Dihedral group
Sep
8
comment Semidirect product structure of Dihedral group
What is $p$? Is it $2$?
Sep
8
comment Equal on an open subset implies equal on the whole space?
@darijgrinberg: That should be an answer.
Sep
4
revised About group actions
added 17 characters in body
Sep
4
comment About group actions
Yea, I wrote the second paragraph before they posted that link, I agree that order is probably not what they're talking about.
Sep
4
answered About group actions
Sep
4
answered How did they derive the image from kernel?
Sep
4
comment Is this basic fact about prime pairs obvious?
@lulu: The question is about the relationship between the sets $A_p$ and $A_q$ when $p, q$ is a pair of prime numbers. That's what the "prime pair" in the title refers to.
Sep
4
answered Is this basic fact about prime pairs obvious?