Johannes Kloos
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 Oct 28 reviewed Approve Determining whether a certain element in a tensor product is zero Oct 28 reviewed Close $f : [a, ∞) → R$ is a continuous function. If $\lim_{x→∞} f (x) = L$, prove that $f$ is uniformly continuous on $[a, ∞)$. Oct 28 comment Predicate Logic - Is my answer correct? @dfeuer: I suppose that comes from the OP's edits. Oct 27 comment Predicate Logic - Is my answer correct? If you have $\models$ available, write the whole thing as $\{ (\forall x, A(x) \implies \neg B(X)), B(C) \} \models \neg A(C)$. The mentioned rules give you the result you want. Oct 27 comment Predicate Logic - Is my answer correct? [...cont'd] So, one way of formalizing your statement would be $(\forall x, A(x) \implies \neg B(x)) \implies B(C) \implies \neg A(C)$. Another would be $((\forall x, A(x) \implies \neg B(x)) \land B(C)) \implies \neg A(C)$. (Small remark on the side: actually, the statement is slightly different, and should be formulated using $\models$, but I don't known if you have come far enough for that already). Oct 27 comment Predicate Logic - Is my answer correct? It may be helpful to think about what the different symbols actually mean. Basically, $A \land B$ means that both $A$ and $B$ are true (usually independently of each other). This means that to prove $(\forall x, A(x) \implies \neg B(x)) \land (B(C) \implies \neg A(C))$, you would have to prove two statements, one being $\forall x, A(x) \implies \neg B(x)$ - this is probably not what you want. On the other hand, $\implies$ can be used to build arguments with assumptions and conclusions: $A \implies B$ means "assuming $A$, $B$ is true" or "Suppose $A$. Therefore $B$." [cont'd...] Oct 27 comment Predicate Logic - Is my answer correct? Strictly speaking, this seems to be a correct answer. But two questions remain: 1. What on earth do all these commas mean? 2. Why is there a lone $B(C)$ floating around in you formula? Oct 27 answered Predicate Logic - Is my answer correct? Oct 27 revised Predicate Logic - Is my answer correct? TeXified. Also made sure that my edit didn't make the text incoherent. Oct 27 comment Predicate Logic - Is my answer correct? If you want to write well-formatted formulas, you should consider using MathJax, see here: math.stackexchange.com/help/notation. I edited your question to use it - look at the source to see what I've done. Oct 27 comment Predicate Logic - Is my answer correct? Hi, I don't quite understand you notation. It take it that $-A(C)$ means $\neg A(C)$, i.e., not $A(C)$). Is $A(x) = -B(x)$ supposed to be $A(x) \implies \neg B(x)$ or $A(x) \iff \neg B(x)$? Oct 27 reviewed Looks OK Prove that f is differentiable at $0$ Oct 27 reviewed Reviewed getting T(n) when I get bigTheta complexity from recurrence relation Oct 27 revised getting T(n) when I get bigTheta complexity from recurrence relation Some minor grammtical corrections, TeXified. Oct 27 reviewed No Action Needed How is a system of axioms different from a system of beliefs? Oct 25 reviewed Approve What is my grade percentage Oct 25 reviewed Close Integration by Symmetry Oct 25 reviewed Leave Open How do I prove inequalities and one-to-one function? Oct 25 reviewed Leave Open Finding a counterexample in model theory Oct 25 reviewed Close Topology on cartesian product and product topology