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Jan
8
revised Definition of Dirac Delta function on the surface of a unit sphere
deleted 7 characters in body; edited title
Jan
8
comment Is there a symbol for plus and minus as opposed to plus or minus?
@TitoPiezasIII: The closest I could come up with is Module[{R},R[s_]:=(2 b^3-9 a b c + s Sqrt[-4(b^2 - 3 a)])^(1/3); (2/3a)(R[+1]+R[-1])]
Jan
8
awarded  Good Answer
Jan
8
comment Prove that row rank of a matrix equals column rank
Why did you not add your answer to an existing question, instead of writing a duplicate question?
Jan
8
answered Basis for set of matrices with trace not equal 0
Jan
8
awarded  Nice Answer
Jan
7
answered Is there a symbol for plus and minus as opposed to plus or minus?
Jan
2
answered Is it possible to draw this picture without lifting the pen?
Jan
2
comment Is it possible to draw this picture without lifting the pen?
You omitted an important (but obvious) condition: The graph must be connected!
Dec
21
answered Even + Odd Function
Dec
21
answered Have anyone ever thought of continuous analog Turing machine?
Dec
21
comment Have anyone ever thought of continuous analog Turing machine?
As far as I know, those analog computers were not universal computers, but purpose-built for specific problems. The point of the Turing machine is that it is universal.
Dec
20
answered When is a mobius transformation its own inverse?
Dec
20
revised Find the value of following complex number
edited title
Dec
20
comment $A \cap B$ = $A \cup B \iff A = B$
@dreamin: $A\subset A\cup B$ is a property of $\cup$. $A\cup B=A\cap B$ by assumption. $A\cap B\subset B$ is a property of $\cup$. Note that this proves only one direction, but the other direction works essentially the same.
Dec
19
comment A weighted measure of international diversity
What exactly is your definition of a "valid method"?
Dec
19
revised Zeroes of sin(x)
fixed formatting
Dec
19
comment Description of the universe of sets
I think he is describing the von Neumann universe. In particular, I think with the "situation in which all the stages in the collection are completed" he refers to the stages corresponding to limit ordinals.
Dec
19
comment Problem solving rolling dice
What are the rules exactly? Does your partner tell you that you have rolled at least 9 as soon as this is true? Or could he remain silent until after you've done a few further rolls (after which you of course still have rolled at least 9)?
Dec
19
comment What is ${\rm Im}(z)+{\rm Re}(z)=1$?
Hint: $z=x+\mathrm iy$. What does the equation $x+y=1$ describe?