User Phira - Mathematics Stack Exchange

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	12,169 reputation	bio	website		visits	member for	2 years, 1 month
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Result is valid if we change $0$ by $a \in \mathbb{R}^*$?

homework real-analysis

oct 10 '11 at 18:32 Davide Giraudo 56.2k

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1

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201

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Why are variables lowercased?

oct 7 '11 at 16:34 JavaAndCSharp 113

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3

answers

213

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Number of strict total orders on $N$ objects

combinatorics order-theory

may 12 '11 at 12:01 Gerry Myerson 85.8k

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2

answers

81

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Solvability of matrix filling

cryptography

may 1 '11 at 21:16 hardmath 7,019

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1

answer

241

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Expressing the given integral in terms of summation

real-analysis analysis integral

may 11 '11 at 13:38 Community♦ 1

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195

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Number of subsets with $n-k$ elements containing at least one of a given set of subsets with $k$ elements

combinatorics

apr 23 '11 at 16:38 Stefan Walter 1,796

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answer

86

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Divisibility, many unknowns

elementary-number-theory divisibility

nov 1 '11 at 12:13 J. M. 38.9k

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1

answer

178

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Mean value theorem proof

homework calculus

oct 7 '11 at 21:49 Sasha 41.4k

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0

answers

129

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Why a spiral is the deformation retract of a plane?

general-topology

oct 28 '11 at 17:41 hxhxhx88 1,015

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265

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What is $\mathbb C[a_1,a_2,a_3,\dots]/a(t)^2$ (where $a(t)$ is $a_1t+a_2t^2+\dots$)?

abstract-algebra generating-functions

nov 8 '11 at 20:25 Community♦ 1

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65

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Monochromatic degenerate triangles in a two-coloring of the plane

combinatorics coloring ramsey-theory

may 18 '12 at 20:47 Ternary 251

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365

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Show either $f$ is constant or $g(z)=0$ for all $z$ in the region

complex-analysis

may 21 '12 at 8:41 Willie Wong♦ 30.6k

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1

answer

110

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Triangle and point inside

geometry

may 24 '12 at 5:58 Michael Hardy 47.9k

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1

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84

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Integral over triple product of spherical Bessel functions

analysis integration

nov 27 at 9:30 joriki 92.5k

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165

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Non-physical Jounce Examples in Nature

calculus derivatives examples-counterexamples

nov 21 at 2:27 Gerry Myerson 85.8k

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153

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Proving that $|CA|+|CB|=2|AB|$ in a general $ABC$ triangle

geometry euclidean-geometry triangle

nov 4 at 18:38 Phira 12.2k

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votes

2

answers

133

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How to prove positive definiteness?

matrices norm

oct 28 at 23:31 littleO 2,190

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265

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How many unique pairs of integers between $1$ and $100$ (inclusive) have a sum that is even?

combinatorics

dec 12 '11 at 6:57 Arturo Magidin 158k

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votes

2

answers

111

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Proof : $2^{n-1}\mid n!$ if and only if $n$ is a power of $2$.

elementary-number-theory proof-strategy proof-writing

nov 30 at 23:02 Community♦ 1

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83

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A be a $3\times3$ real valued matrix such that $A^{3}=I$ but $A \neq I$ .Then trace(A)=?

homework linear-algebra

dec 11 at 9:58 P.. 8,860

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vote

1

answer

55

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Sum of angles in a polygon - Alternative solution

geometry combinatorial-geometry

nov 29 at 20:35 Phira 12.2k

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vote

1

answer

170

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Maximum area for fixed perimeter of a triangle

calculus geometry problem-solving

dec 8 at 17:56 lab bhattacharjee 28.6k

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0

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133

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Solve $x^x=2x$ for $x$, s.t. $x\in\mathbb{C}$

algebra-precalculus exponentiation

may 27 '12 at 14:39 Gigili 3,151

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321

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Simplify this expression with nested radical signs

algebra-precalculus

jun 8 '12 at 19:29 Community♦ 1

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179

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Is the function $f(x) = (x^2, \sin x)$ onto or one-to-one?

functions elementary-set-theory

oct 25 '11 at 20:44 Asaf Karagila 90.7k

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vote

1

answer

101

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Partition problem of set

graph-theory

oct 23 '11 at 12:17 Phira 12.2k

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1

answer

108

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Structure of $k$ as $k[X]$-module

modules

oct 28 '11 at 23:38 Thomas Andrews 29.6k

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vote

2

answers

311

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Euclidean algorithm to find the GCD

homework algorithms elementary-number-theory

apr 22 '11 at 18:41 Ross Millikan 83.2k

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1

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53

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Error in Bell series of arithmetic functions

elementary-number-theory

apr 23 '11 at 15:13 Phira 12.2k

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6

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297

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Solving indetermination in limit

calculus limit

dec 15 at 0:58 Bruno Garcia 57

Phira

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