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2h
reviewed Approve Finding Both Missing Co-ordinates in distance formula
17h
revised A property for an ODE
deleted 420 characters in body
21h
reviewed Close an objective question from functional analysis
21h
comment Comparing metric tensors of the Poincare and Klein disk models
Those notations with $dx$ have to be interpreted formally, treating differential forms as if they were numbers. The symbol $dx_i^2$ reads in more rigorous notation as $dx_i\otimes dx_i$, of this I am entirely sure. The symbol $x\cdot dx$ might be a synonim of $\sum_i x_idx_i$. And similarly $\lvert dx\rvert^2$ might be a synonim of $\sum_i dx_i^2$.
23h
answered A property for an ODE
1d
comment A property for an ODE
@DemetriP: Of course. The problem here is exactly the singularity at $t=0$.
1d
comment A property for an ODE
But there is a singularity at $t=0$. Did you take this into account?
1d
answered Convert from complex exponentials to sinusoids
2d
comment Laplace Operator in $3D$
This is a nice observation that should be made more often. After all, that's where the $r^{-(n-1)}, r^{n-1}$ terms in $$\Delta u= \frac{1}{r^{n-1}}\partial_r(r^{n-1}\partial_r )+\dots $$ come from.
2d
comment If each term in a sum converges, does the infinite sum converge too?
This is a good answer, making it clear that the famous Weierstrass's M-test is part of the principle of dominated convergence. (I liked the use of the word "principle" instead of "theorem" here).
2d
awarded  Proofreader
2d
reviewed Close nonempty disjoint closed subsets of $\mathbb{R}^{n}$
2d
reviewed Close Area of a curve $\frac{x^2}{4}+\frac{(y-3)^2}{9}=1$
2d
reviewed Approve trigonometry: prove that (tanA)(tanB)+(tanB)(tanC)+(tanA)(tanC)=1
2d
reviewed Approve Determination of quartic Gauss sums
May
15
answered Purely algebraic proof of the trigonometric inequalities
May
14
comment Fourier transform not surjective using oppen mapping theorem.
@LeBtz: You are welcome. The main idea, as you righfully found, is that the function $\sin x /x$ has infinite $L^1$ norm and its Fourier transform has finite $L^\infty$ norm.
May
14
comment Fourier transform not surjective using oppen mapping theorem.
@LeBtz: It works.
May
14
answered Holomorphic function definition. Am I missing something very obvious?
May
14
reviewed Leave Open How can I use limits in everyday life?