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313/80 answers
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14h
comment Relation between being epic and having a “full” image.
The answer to your question is yes.
Apr
15
comment every category is equivalent to its universal cover
Aha, ok, you convinced me :)
Apr
15
answered Is GRP a subcategory of SET, or not?
Apr
15
revised Why do counits go that way?
deleted 18 characters in body
Apr
15
answered Why do counits go that way?
Apr
15
comment The inclusion $\mathbb Z \to \mathbb Q$ is an epimorphism
No. $R$-modules are very nice for any ring $R$.
Apr
15
answered Volume of a parallelepiped, given 8 vertices
Apr
15
comment every category is equivalent to its universal cover
The notation $(A,(\phi_a)_{a\in A})$ is not entirely clear. So, the thing is that all objects of such an indiscrete subcategory $A$ are isomorphic to each other, and hence $A$ can be mapped to any of its object. Cannot an initial object be mapped to the empty subcategory?
Apr
15
comment Volume of a parallelepiped, given 8 vertices
Not any three would do it, see the comments.
Apr
13
answered Solving Complex Eigenvalues
Apr
13
comment Find basis for kernel and matrix representation
You substitute $p=x^2$ in the place of $p$, so evaluate $p(-1)$, and while evaluating you substitute $x=-1$ into $p=x^2$.
Apr
13
answered Find basis for kernel and matrix representation
Apr
11
revised Some proprieties of the matrix $A^\top A$
deleted 25 characters in body
Apr
11
answered Some proprieties of the matrix $A^\top A$
Apr
11
answered Generating function for a sequence
Apr
11
comment What are the semisimple $\mathbb{Z}$-modules?
But $\Bbb Z$ is not simple.
Apr
11
comment Explicit bijection between $\mathbb Q$ and $\mathbb Z \times \mathbb Z$?
Well, with my comment it can give a full answer.
Apr
11
comment Bijection in the Yoneda Lemma
What alternative do you mean? Maybe the formula for its inverse? Or what else?
Apr
11
comment Power set functors preserve monicness
I think you answered something that was not asked in the original question..
Apr
11
comment Is $a$ is transcendental over Q if Q(a) = Q(x)? I know the converse is true.
What are you uncertain of?