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BrianO
  • Member for 8 years, 6 months
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28 votes
Accepted

Is the negation of a non-theorem a theorem?

23 votes
Accepted

Is every relation which is transitive and symmetric also reflexive?

20 votes

Quantifier: "For all sets"

18 votes

Absolute value and max/min function: why $a + b + |a - b|=2\max(a,b)$?

16 votes

Can a set be neither open nor closed?

14 votes
Accepted

Inverse of $A^{-1}+B^{-1}$

11 votes

Why is the Axiom of Infinity necessary?

10 votes

Why is the Axiom of Pairing required?

9 votes
Accepted

Is there any well-ordered uncountable set of real numbers under the original ordering?

8 votes

What's the point of allowing only quantification of variables in first-order logic.

8 votes
Accepted

Predicate Logic Expression: "Nobody loves anybody."

8 votes
Accepted

Sum of monotone functions

8 votes

Counterexample, union of intersections, intersection of unions

7 votes
Accepted

Logical formula of definition of linearly dependent

7 votes

Is the set of all topological spaces bigger than the set of all metric space?

7 votes

mathematical symbol for a new member replacing a member in a set

7 votes

Intuitive meaning of the concept “computable”

7 votes

Please Explain Kuratowski Definition of Ordered Pairs

7 votes

$\infty$ and $-\infty$ are to $\aleph_0$ / $\beth_0$ as "what" is to $\beth_1$?

7 votes

Is this alternative notion of continuity in metric spaces weaker than, or equivalent to the usual one?

7 votes

How can a Cauchy sequence converge to an irrational number?

6 votes
Accepted

Use of directed sets in the definition of nets in topology

6 votes

Why might Dieudonne have been "begging the question" by appealing to second-order Peano Axioms?

6 votes

If $f:X\rightarrow Y$ and $V\subseteq Y$, does there exist $U\subseteq X$ such that $f(U)=V$?

6 votes

If a formula $φ$ contains at most one occurrence of any sentence letter, then $φ$ is not a tautology.

6 votes

Differentiable function on an interval containing 0

6 votes

Can I use greek letters such as alpha to denote a set?

6 votes
Accepted

Laws of logic Assertion/Reason format

6 votes

Implication in mathematics - How can A imply B when A is False?

5 votes
Accepted

Limits of transfinite numbers

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