Ink's user avatar
Ink's user avatar
Ink's user avatar
Ink
  • Member for 11 years, 8 months
  • Last seen more than 3 years ago
43 votes
Accepted

The preimage of continuous function on a closed set is closed.

36 votes

Finite union of compact sets is compact

28 votes

Prove that the additive inverse of an odd integer is an odd integer

14 votes
Accepted

Limit point and interior point

12 votes

Prove that this is no real number such that $x \leq a$ for all real $x$.

11 votes
Accepted

Application of Liouville's Theorem

11 votes

“$f$ is a function from $A$ to $B$” vs. “$f $is a function from $A$ into $B$”?

9 votes

Rudin Theorem 3.27

8 votes

Complete undergraduate bundle-pack

8 votes
Accepted

A subgroup containing a kernel of a group homomorphism into an abelian group is a normal subgroup.

8 votes
Accepted

Need help understanding Erdős' proof about divergence of $\sum\frac1p$

7 votes

(Simple) Examples on Non-Commutative Rings

7 votes

What is the difference between vector components and its coordinates?

7 votes
Accepted

Interval iff image is interval

7 votes
Accepted

$A$ is a subset of $B$ if and only if $P(A) \subset P(B)$

6 votes

Find a metric space X and a subset K of X which is closed and bounded but not compact.

6 votes
Accepted

Is this claim true that $g\circ h$ is bijection?

5 votes

Let $S=\lbrace a+bi \in \mathbb{C} \colon a^2+b^2=1 \rbrace$. Show that $\mathbb{R}/\mathbb{Z}$ is isomorphic to $S$

5 votes
Accepted

A question on open mappings

5 votes
Accepted

How to show a subset is part of another set?

5 votes
Accepted

How to Prove the Dimension of the Annihilator

4 votes

Intermediate Value Theorem and Discontinuous Functions

4 votes
Accepted

Hausdorff space and compact subspaces

4 votes
Accepted

Proving a lemma - show the span of a union of subsets is still in the span

4 votes

Show that H is a subset of the normalizer

4 votes

Determine if the Gaussian Integers $\mathbb{Z}[i]$ and $\mathbb{Z}\times\mathbb{Z}$ are isomorphic rings

4 votes

Prove that $f$ is not continuous for any value in $\mathbb R$.

3 votes

Real Analysis: Is $\emptyset$ a open set in $X$?

3 votes
Accepted

Prove that there is a $c \in [a,b]$ such that $f(c)=0$

3 votes

Show that the ideals of $\mathbb Z$ are principal.

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