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132108
bio website math.ethz.ch/~blatter
location Switzerland
age 78
visits member for 3 years, 11 months
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Jul
5
revised Interpreting higher order differentials
edited body
Jul
4
answered Is this notation $\prod\limits_{k=k}^n k $ valid for expressing this product? (ways of arranging $k$ things in $n$ places)
Jul
4
answered Divergent of a vector field on a sequence of spheres
Jul
4
comment Showing a two-variable function is continuous
You don't need to determine the $\min$ of $g(\theta):=\cos^4\theta+\sin^4\theta$. It is sufficient to note that $g$ is continuous, periodic, and $>0$ for all $\theta$.
Jul
4
comment Prove that $[0,1]$ is not isometric to $[0,2]$.
It is not true that necessarily $\{f(0),f(1)\}=\{0,2\}$.
Jul
3
answered Interpreting higher order differentials
Jul
2
revised Sufficient conditions for differentiability of multivariate functions
added 75 characters in body
Jul
2
answered Sufficient conditions for differentiability of multivariate functions
Jul
1
comment Element of a Singleton (set with one element) notation
A proposal: Use inverted braces to "unpack" $y$, like so: $\ y=\}X\{\ $.
Jul
1
answered Why Fourier transform owns two different signs?
Jun
30
comment Existence of Riemann Integral
Concerning "I do not wish to use continuity": Do we have to introduce $\sin$ from first principles, e.g., prove that it satisfies a Lipschitz condition?
Jun
30
comment Characterization of differentiable functions from $\mathbb{R}^m$ to $\mathbb{R}^n$.
The formula in my answer and the statement in your comment are equivalent.
Jun
30
answered A proof (result) verification of a statement in metric-spaces
Jun
30
answered Application of Liouville's theorem exercise
Jun
29
comment Why is the symbol ζ sometimes used in a complex function?
When studying functions of one real variable one uses $x$, $t$, or $r$ (and other letters) as names for the independent variable. In the same way one uses $z$, $\zeta$, or $w$ (and other letters) as names for a complex independent variable.
Jun
29
answered Characterization of differentiable functions from $\mathbb{R}^m$ to $\mathbb{R}^n$.
Jun
28
answered Heat Equation derivative in terms of Laplace
Jun
28
revised points with integer coordinates inside triangles in $\Bbb{R}^3$
added 1063 characters in body
Jun
28
revised How find this maximum of the $\sin^2{\theta_{1}}+\sin^2{\theta_{2}}+\cdots+\sin^2{\theta_{n}}$
added 78 characters in body
Jun
28
answered points with integer coordinates inside triangles in $\Bbb{R}^3$