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seen Dec 15 at 14:59

Sep
19
awarded  Yearling
Jan
13
comment If $A \hookleftarrow B \to R$ each contain $R$, is $R\to A\otimes_B R$ injective?
I had also found the similar example $B=R[x]$, $A = B[x^{-1}]$, and $B\to R$ sending $x\mapsto 0$. Thanks for tying off this loose question!
Jan
13
accepted If $A \hookleftarrow B \to R$ each contain $R$, is $R\to A\otimes_B R$ injective?
Dec
12
answered Limit of series $4\left( \frac {1}{8}+\frac {1}{12}\right) +6\left( \frac {1}{24}+\frac {1}{36}\right) +\ldots$
Dec
12
comment Prove that if $7$ divides $6^n + 1$ then $n$ is odd
Just to note: You have written the inverse, not the contrapositive. The contrapositive would be "If $n$ is not odd, then $7$ does not divide $6^n + 1$."
Sep
20
accepted Are automorphisms of extensions trivial?
Sep
20
comment Are automorphisms of extensions trivial?
In fact, $0\to \mathbb{Z}/(2) \to \mathbb{Z}/(4) \to \mathbb{Z}/(2) \to 0$ with the automorphism $f:a\mapsto -a$ also works.
Sep
20
comment Are automorphisms of extensions trivial?
Specifically, $0\to \mathbb{Z}/(3) \to \mathbb{Z}/(9) \to \mathbb{Z}/(3) \to 0$ with the automorphism you give. Excellent, thanks!
Sep
20
asked Are automorphisms of extensions trivial?
Sep
19
awarded  Yearling
May
1
answered Help understanding why a block code can correct up to (d-1)/2 errors.
Apr
12
comment The last few digits of $0^0$ are $\ldots0000000001$ (according to WolframAlpha).
"But the limit is $1$ if $f,g$ are both analytic..." What about $f(x)=0$, $g(x)=x$? I'm not sure what the missing condition is.
Apr
12
comment Cross product with orthonormal basis
It does if you meant to write $(f_{u_1}(p),f_{u_2}(p),f_{u_3}(p))\times(g_{u_1}(p),g_{u_2}(p),g_{u_3}(p))$. Then you're taking the cross product of the same two vectors on each side of the equation.
Apr
12
answered Expectation value of pure state in quantum mechanics
Apr
12
answered Is $Ϝ$ an equivalence relation?
Feb
8
answered Given a diagonalizable matrix A, must $A^2$ and $A$ be row equivalent?
Nov
20
comment How do we represent this event?
The CDF is the probability that $M$ is any value up to $x$: $P(M < x) = 1 - P(M\geq x) = 1 - (1-x)^2$. The PDF is the derivative of the CDF: $d(1-(1-x)^2)/dx = 0 - 2(1-x)^1 (-1) = 2(1-x)$.
Nov
19
comment How do we represent this event?
Both -- the area in the plane is the probability of the corresponding event, since $X$ and $Y$ are independent and uniform. I've edited to elaborate.
Nov
19
revised How do we represent this event?
added 358 characters in body
Nov
19
answered How do we represent this event?