Hagen von Eitzen
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136,345
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# 136,345 Reputation

278 today
 +40 4 hours ago 4 events Proving a set to be countably infinite. +35 3 hours ago 3 events Let $f\colon [a,b]\to\mathbb R$ be twice differentiable and assume $f(a)=f(b)=0$ and $f''(x)<0$ for all $x$ in $(a,b)$. Show that $f(x)>0$ on $[a,b]$. +35 4 hours ago 3 events Proving something is not a Normal Extension +25 5 hours ago 2 events quotient of lattices, why of finite length? (about a statement in Local Fields of Serre) +20 4 hours ago 2 events Prove that $A$ is countable. +20 6 hours ago 2 events Examples of Non-Faithful Group Actions +15 10 hours ago accept understanding of Artin's proof of “$A_n$ is generated by $3$-cycles” +15 13 hours ago accept How does the first fundamental theorem of calculus guarantee the existence of antiderivatives of functions? +15 19 hours ago accept Approximating length of a curved line based on Begining and End points of line +10 3 hours ago upvote Two pawns walking in a complete graph +10 5 hours ago upvote $\{\,x \in I: \phi'(x)$ $\text{does not exist}\,\}$ is at most countable. +10 5 hours ago upvote Word problem help? +10 19 hours ago upvote How many scientists can survive? +10 20 hours ago upvote Which is greater: $1000^{1000}$ or $1001^{999}$ +10 21 hours ago upvote Cardinality of a minimal open cover of the disc -2 4 hours ago downvote Transformation of a function into a power series
445 yesterday
 +150 04:18 bounty Prove a relationship involving floor functions +95 13:50 5 events Differentiate polynomials in $\mathbb{Z}_2[x]$ +40 12:13 4 events Log of many Logs +35 12:10 3 events Prove by induction $n^{1/n} ≤ \frac{n+1}{2}$ +30 17:37 3 events understanding of Artin's proof of “$A_n$ is generated by $3$-cycles” +30 16:49 3 events Finding the fallacy in this wrong limit computing result +25 17:42 2 events Systems of Congruences Modulo a Prime +20 07:00 2 events Proving equivalence of sets +10 18:32 upvote Ball bouncing in a box, will it meet a vertex. +10 18:08 upvote product of path connected space is path connected +2 18:36 upvote How can a piece of A4 paper be folded in exactly three equal parts? 21:26 3 events How does the first fundamental theorem of calculus guarantee the existence of antiderivatives of functions? -2 21:38 2 events How many scientists can survive?
180 2 days ago
 +30 18:04 3 events Let G be a group. Use the FHT (Fundamental Homomorphism Theorem) to prove that the quotient group G/{e} is isomorphic to G. +25 18:24 2 events Proof DES is injective - is this a valid argument +20 21:14 2 events Cardinality of a minimal open cover of the disc +20 18:42 2 events Prove a relationship involving floor functions +20 18:09 2 events What is the expected number of people who are shorter than both of their immediate neighbors? +20 11:07 2 events Determining half life without logs, given only reduction undergone and total time taken +15 21:22 accept Vector times symmetric matrix +10 18:56 upvote Can every proof by contradiction also be shown without contradiction? +10 14:35 upvote Any hint about solving this monster determinant? +10 02:46 upvote Approximating length of a curved line based on Begining and End points of line
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