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Apr
22
comment Weird subfields of $\Bbb{R}$
@temo The question is quite old, so I don't really remember. I guess it was in some book on linear algebra or on some other topics in real analysis
Apr
11
comment I've found a MATLAB plot in a book and want to know which command the authors used for the plot
If you need to swap axes just change the role of X and Y and transpose ut: surf(Y,X,ut')
Apr
11
comment I've found a MATLAB plot in a book and want to know which command the authors used for the plot
If the graph is entirely black, then your ut contains only one value. Probably there may be a mistake in the computation of ut.
Apr
11
comment Computing a matrix from its exponential
Is your matrix diagonalizable? Do you know $e^{tA}$ or just $e^A$?
Apr
11
answered I've found a MATLAB plot in a book and want to know which command the authors used for the plot
Apr
10
comment I've found a MATLAB plot in a book and want to know which command the authors used for the plot
I guess that since you're reading the book (which is about Matlab applications) you must learn how to do it from it... Anyway, there's no command which plots you the solution right away. You need to construct a script which does it... Continue reading the book (by the way, you could mention its title... if you want someone to help). The code might be presented somewhere
Mar
10
awarded  Popular Question
Mar
2
answered FreeFem++ code approximating the Laplace equation
Feb
28
comment $f(x)$ decreasing and positive implies $f'(x)$ converges to 0?
Is your limit point $\infty$? If so, then if $f(x)$ does not converge to zero what makes you think that $xf(x)$ can converge to zero?
Feb
21
awarded  Yearling
Jan
21
awarded  Popular Question
Jan
7
awarded  Nice Question
Dec
12
awarded  Favorite Question
Dec
10
comment Cutesy Applications of Fermat's Last Theorem (or others)
From the other part of the product $(a^n-b^n)^2+(b^n+c^n)^2+(a^n+c^n)^2 = 0$.
Dec
10
comment Cutesy Applications of Fermat's Last Theorem (or others)
One of the factors given by the equation is $a^n+b^n-c^n$ which by FLT is never zero.
Nov
18
reviewed Approve problem on divisiblity
Nov
17
comment Proving that a Finite Field Over Its Prime Field Is Galois
I don't remember making this review. Galois theory is not among my favorite subjects neither... Maybe your answer got mixed up with something because it is too short, like a comment.
Nov
15
comment Minimizing $\int_{0}^{1} (1+x^2)f(x)^2 dx$ for $f(f(x)) = x^2$
@mick: No one's voting to close because a source is missing, but the fact that you are the source and you don't know the solution is not very encouraging. I asked since some problems taken from high profile contests or exercices from advanced books are not easily solved if you don't have some context. Furthermore, if you just made up the problem, it may not even be possible to solve it...
Nov
15
comment Minimizing $\int_{0}^{1} (1+x^2)f(x)^2 dx$ for $f(f(x)) = x^2$
What's the source of this problem?
Nov
15
comment Minimizing $\int_{0}^{1} (1+x^2)f(x)^2 dx$ for $f(f(x)) = x^2$
@AlfredYerger: I think $f^2$ means $f$ squared. If the superscript refers to composition like you say, then you just replace by $f\circ f$ by $x^2$ and you don't have anything to optimize.