Christoph's user avatar
Christoph's user avatar
Christoph's user avatar
Christoph
  • Member for 10 years, 8 months
  • Last seen more than a month ago
48 votes
Accepted

Is the determinant differentiable?

38 votes

What is the difference between Cauchy and convergent sequence?

38 votes
Accepted

The boundary of an $n$-manifold is an $n-1$-manifold

20 votes
Accepted

What is an additive functor?

20 votes

Calculus: Why do we ignore dx?

19 votes
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Starting sentences with mathematical symbols.

17 votes
Accepted

$\Bbb{Q}$ is not a finitely generated $\Bbb{Z}$-module

15 votes
Accepted

Is it always true that $\mathrm{int}(\ A \setminus \mathrm{int}(A)\ ) = \emptyset$?

14 votes
Accepted

Finding the coordinate vector relative to a given basis

14 votes
Accepted

Probability that an integer number having Poisson distribution is even

13 votes
Accepted

What is the meaning of "well-defined" and how to prove something is "well-defined"

13 votes
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Can the sum of continuous functions be discontinuous?

12 votes
Accepted

Historic proof of the area of a circle

11 votes

How to determine the side on which a point lies?

10 votes
Accepted

Why $\dim(\hom(V,W))=\dim(V) * \dim(W)$?

9 votes
Accepted

Difference between Null set and empty set

9 votes

Find all homomorphisms from $\mathbb Z_4\to\mathbb Z_2\oplus\mathbb Z_2$

9 votes

Is the word "empty" in set theory different from the word "empty" in ordinary language?

9 votes

Understanding short exact sequences

8 votes

non linear transformation that satisfies $T(cx) = cT(x)$

8 votes

How many vectors are needed to define a plane in n dimensions?

8 votes
Accepted

What does Structure-Preserving mean?

8 votes
Accepted

Is the surface of the body/skin homeomorphic to a torus?

8 votes
Accepted

What are the possible eigenvalues of a linear transformation $T$ satifying $T = T^2$

8 votes

Under what conditions can the symmetric group be isomorphic to the abelian group?

7 votes
Accepted

the Gaussian integers are isomorphic to $\mathbb{Z}[x]/(x^2+1)$

7 votes

What is the difference between diffeomorphism and isomorphism?

7 votes

Usage of "commute"/"commutative"

7 votes
Accepted

A new type of numbers?

7 votes
Accepted

Why is the notation $A\setminus B$ preferred over $A-B$?

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