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visits member for 2 years, 9 months
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Interested in elementary algebra enter image description hereproblems, and teaching.


1d
answered Show that $S=\mathbb{Q} \cap [0,2]$ is not compact
1d
comment Property of SO(3)
This is worked out in Michael Artin's textbook "Algebra".
1d
revised An example of a family of projective irreducible curves
added 697 characters in body
1d
comment An example of a family of projective irreducible curves
OOPS! I missed reading that requirement.
2d
answered An example of a family of projective irreducible curves
2d
comment Infinite group with finite order elements
@Marc: I read your comment ignoring the parenthesis, and interpreted it as saying "No, it is not countable", and rushed with the above comment!
2d
comment Infinite group with finite order elements
It is quotient of the group of positive rationals, hence countable.
2d
comment Finding all irreducible representations of dihedral group $D_8$
In your question there is an answer: you define $D_8$ as the group of symmetries of a square, which realises each element as a linear automorphism of the plane that preserves the square.
2d
answered Infinite group with finite order elements
2d
comment Why does Gaussian elimination not preserve similarity of a matrix?
@Algebraic Pavel Not exactly.He asks "must one apply both the operation and its inverse operation simultaneously?". When one applies $E$ on the left one should also multiply by $E^{-1}$ on the right.
2d
answered Ideal of $TV$ which trivially intersects $V$
2d
comment Possible integer roots of polynomial with real coefficents
It is well known that a polynomial of degree $n$ has $n$ roots, even when we count complex ones and repetitions. Why this hard way to prove finitely many integer roots?
2d
revised Finding $f(i)$ for an Entire Function $f$ that Maps a Line to a Subset of Itself and Sends $1$ to $0$.
self-explanatory
2d
answered Finding $f(i)$ for an Entire Function $f$ that Maps a Line to a Subset of Itself and Sends $1$ to $0$.
2d
answered Suppose $f(g(t))$ is differentiable. Does this neccesarily imply that $g(t)$ is differentiable?
2d
comment General form of an element of the othogonal basis of $q$
Ok, I understand now, removed my downvote.
2d
comment General form of an element of the othogonal basis of $q$
Your definition of $q$ equates a matrix to a number, which is meaningless. (It is not even its determinant.) Also the basis you have written repeats the same vector.
Jan
29
suggested rejected edit on Cuscs of a subgroup of $\Gamma$
Jan
29
answered Lattice of integers $\mathbf{Z}$ in $\mathbb{R^2}$
Jan
28
comment Vector Spaces and Simple Modules
Choose an $R$-submodule $W\subset V$ that has least possible dimension as an R-vector space. When we have a finite-dimensional vector space any proper subspace has strictly lower dimension.