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a real pythagorean


2d
comment Joke explanation: “a comathematician is a device for turning cotheorems into ffee”
@goblin you're totally right, but in other contexts the 'co' could switch the direction, and in the dual joke it is switched.
2d
awarded  Enlightened
Aug
17
awarded  Nice Answer
Aug
17
comment Show that $A \cup B$ and $C$ are independent as well
Start at the definition of being independent.
Aug
17
revised Joke explanation: “a comathematician is a device for turning cotheorems into ffee”
added 11 characters in body
Aug
16
answered Joke explanation: “a comathematician is a device for turning cotheorems into ffee”
Aug
16
answered Union of subgroups is subgroup
Aug
16
comment Some wedge product computation
A basic property of exterior product is that $w\land w=0$ for all $w$.
Aug
16
revised Help in this characterization of the gaps of the symmetric numerical semigroups
added 126 characters in body
Aug
16
revised Help in this characterization of the gaps of the symmetric numerical semigroups
added 126 characters in body
Aug
16
revised Help in this characterization of the gaps of the symmetric numerical semigroups
added 222 characters in body
Aug
16
comment Help in this characterization of the gaps of the symmetric numerical semigroups
Yes, $l_g=2g-1$ is meant to be used. However, the other direction seems not true (neither in your counterexample): if $N=\{2,3,\dots\}$ then $g=2$, and the gaps and nongaps are also symmetric to $3=2g-1$.
Aug
15
answered Help in this characterization of the gaps of the symmetric numerical semigroups
Aug
12
answered Are $i,j,k$ commutative?
Aug
12
comment Which of the following relations are functions of q?
Is there some domain given for $q$? E.g. something like $q>0$ or $q\in\Bbb R$.
Aug
10
comment Tensor products over monoids : Element structure
What do you have in mind for the case when $A$ is a group?
Aug
9
awarded  algebra-precalculus
Aug
6
comment Interior product between differential forms and vector fields
Well, yes a 1-form $\omega$ is a linear function of $X$, satisfying $dx(\partial_x)=1$ and $dx(\partial_y)=dx(\partial_z)=0$. Similarly, for a 2-form, all you have to know is $$(dx\land dy)\big(\partial_x,\partial_y\big)=1$$ and that $dx\land dy$ is antisymmetric.
Aug
6
comment Interior product between differential forms and vector fields
Well, $3\cdot 3=9$..
Aug
6
comment If A Is An Invertible Matrix $F^{n*1}$ Is The A Colmuan Span
Yes. You can rewrite the second statement as 'the rank of $A$ is $n$', which must hold if $A$ is $n\times n$ invertible.