WimC

 114 Why is $\frac{987654321}{123456789} = 8.0000000729?!$ 57 Can every proof by contradiction also be shown without contradiction? 54 Is there a simple, constructive, 1-1 mapping between the reals and the irrationals? 50 Prove that $\log(n) = O(\sqrt{n})$ 34 Making 400k random choices from 400k samples seems to always end up with 63% distinct choices, why?

### Reputation (24,527)

 +10 Let $a_1,a_2,\cdots,a_n$ be n numbers such that $a_i$ is either 1 or -1.If $a_1a_2a_3a_4+\cdots+a_na_1a_2a_3=0$ then prove that 4|n. +10 Bound on derivative of a holomorphic function +10 Cyclic vector implies commuting linear operator is a polynomial +10 Image of koebe map

### Questions (5)

 9 Irreducibility test in a number field 5 Range of i.i.d. normal random variables 4 Square on graph of cubic 4 Fitting a surface to 2D measurements 2 In-place inverse of DFT?

### Tags (268)

 297 complex-analysis × 112 116 arithmetic × 2 251 calculus × 63 115 integration × 23 219 real-analysis × 52 115 rational-numbers × 2 178 inequality × 51 111 trigonometry × 25 127 sequences-and-series × 48 90 linear-algebra × 39

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 Mathematics 24,527 rep 23063 Cross Validated 216 rep 24 MathOverflow 106 rep 2 Physics 101 rep Stack Overflow 101 rep

 Yearling × 7 Popular Question Nice Answer × 30 Guru × 2 Enlightened × 6 Generalist Curious integration Revival × 4 Great Answer

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