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bio website mathproblems123.wordpress.com
location Chambery, France
age 26
visits member for 3 years, 9 months
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Third year Phd student at Universite de Savoie, France. Interests: free boundary problems, PDE, spectral optimization, numerical analysis.


2h
revised $\int_{-1}^{1}|f(t)|dt \geq C\left(\int_{0}^{2}|f(t)|^2\right)^{1/2}$ for polynomials
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2h
answered $\int_{-1}^{1}|f(t)|dt \geq C\left(\int_{0}^{2}|f(t)|^2\right)^{1/2}$ for polynomials
3h
answered How to integrate $1/(u^2 + u^4)$ du?
1d
answered Give the number of solutions of $x+y+z = 30$, for $4 \leq x \leq 14$, $3 \leq y \leq 17$, $10 \leq z \leq 25$.
1d
comment Give the number of solutions of $x+y+z = 30$, for $4 \leq x \leq 14$, $3 \leq y \leq 17$, $10 \leq z \leq 25$.
Where do $x,y,z$ belong? If they are reals, then you cannot give the number of solutions. Are they integers?
1d
comment Visual notion of tangential gradient
If you know what the normal derivative is, then the significance of the tangent derivative is straightforward. If you look at the gradient at a point on the boundary, you can decompose it in two parts: the parts in the normal direction and the rest. That rest is the tangential part.
1d
answered Show that the sequence of functions $(x_n)_{n≥1}$ in $C[0, 1]$ given by $x_n(t) = t^{2n} − t^{3n} , ∀t ∈ [0, 1]$ is bounded
Nov
20
answered Funny interconnection between a triangle and the ellipse inscribed
Nov
19
comment Funny interconnection between a triangle and the ellipse inscribed
Here is the wikipedia article: en.wikipedia.org/wiki/Steiner_inellipse In the end, it mentions that the above theorem as Marden's theorem: en.wikipedia.org/wiki/Marden's_theorem Here is an elementary proof: dankalman.net/AUhome/pdffiles/mardenAMM.pdf
Nov
19
comment Funny interconnection between a triangle and the ellipse inscribed
Interesting :) I guess it is the conic which passes through the midpoints and is tangent to the sides of the triangle. The existence can be proved using affine transformations (from an equliateral triangle). The unicity follows from the fact that it passes through three points and is tangent to three lines. Anyway, it is interesting to see the connection with polynomials :)
Nov
18
comment Integral: $\displaystyle\int\dfrac{\sin^3\theta}{\sqrt{\cos\theta-2}}\,d\theta$
You could replace it with $\sqrt{2-\cos \theta}$. Maybe that's what the original question had.
Nov
18
comment Integral: $\displaystyle\int\dfrac{\sin^3\theta}{\sqrt{\cos\theta-2}}\,d\theta$
If you are working with real numbers, then $\sqrt{\cos \theta -2}$ makes no sense.
Nov
18
answered Dirichlet's principle- task.
Nov
18
comment Dirichlet's principle- task.
I suppose that the second union is for $k \in B$.
Nov
18
answered If the function $f(x_{1}+x_{2})+2\ge f(x_{1})+f(x_{2})$
Nov
18
revised If n $\geq2$, does G necessarily have an element of order $p^2$? Justify your answer.
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Nov
18
comment If n $\geq2$, does G necessarily have an element of order $p^2$? Justify your answer.
@John Yes, but the counterexample still works :)
Nov
18
answered If n $\geq2$, does G necessarily have an element of order $p^2$? Justify your answer.
Nov
18
comment If n $\geq2$, does G necessarily have an element of order $p^2$? Justify your answer.
What is $G$, what is $p$?
Nov
18
answered Sum of eigenvalues of a symmetric matrix