64,365 reputation
141125
bio website math.ethz.ch/~blatter
location Switzerland
age 79
visits member for 4 years, 1 month
seen 4 hours ago

Sep
17
answered Roots of $f(x)=a_0+a_1\cos x+a_2\cos 2x+\dots+a_n\cos nx$
Sep
17
revised How to orient the integration contour when applying the residue theorem?
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Sep
17
comment Drawing a triangle from medians
@user142795: The steps are described below the figure.
Sep
17
answered How to orient the integration contour when applying the residue theorem?
Sep
17
comment Ellipsoidal Decomposition: Finding ellipsoids whose sum contains a given ellipsoid
This might be an interesting problem, but it's absolutely unclear what you mean. E.g., what is $(q,Q)$? What is meant by "sum"? Is doubly covered area counted twice?
Sep
16
comment Explanation of Cauchy's root test / criterion
The Cauchy criterion says that a sequence (of real or complex numbers) converges iff it is a Cauchy sequence. – The partial sums of a series do not necessarily form a Cauchy sequence, as you certainly know.
Sep
16
answered Does $f$ have a local maximum?
Sep
16
awarded  Enlightened
Sep
16
awarded  Nice Answer
Sep
15
awarded  Nice Answer
Sep
15
revised Bug and the grass, when will it climb?
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Sep
15
revised How find this $a$ such $(z_{1}+a)^2+a\overline{z_{1}}\neq (z_{2}+a)^2+a\overline{z_{2}}$
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Sep
15
answered Bug and the grass, when will it climb?
Sep
15
answered How find this $a$ such $(z_{1}+a)^2+a\overline{z_{1}}\neq (z_{2}+a)^2+a\overline{z_{2}}$
Sep
15
awarded  contest-math
Sep
14
comment If Robin's inequality ever fails, are there only finitely many colossally abundant numbers that satisfy it?
Robin's theorem is an "iff" theorem; see here: en.wikipedia.org/wiki/Divisor_function
Sep
14
answered What is the domain of this multivariable function?
Sep
14
comment Maximum square cells in a rectangle
You have to introduce some "glue" into this problem. When the overall width and height are both primes there is no solution fulfilling your conditions.
Sep
14
answered How to compute the following summation?
Sep
14
revised Is any homeomorphism from Riemann sphere to Riemann sphere Mobius transformation?
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