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May
14
comment Let $(X, \mathfrak T)$ be a topological space and suppose that $A$ is a subset of $X$. Then $A'$ is a closed set.
Have you carefully proven that if $A=\mathbb Q$, then no rational number belongs to $A'$? (You're right that the set of irrationals is neither open nor closed)
May
4
comment Simplifying an function with complex numbers
Wait, so you know in advance that both sides are real numbers?
May
4
comment Polynomials of degree less than $n$ that agree at $n$ values
Technically, yeah it is due to the definition of polynomial (over a field), but there is at least one major creative step along the way.
Apr
24
revised Chinese Remainder Theorem - solving a modulo with big numbers
deleted 8 characters in body
Apr
24
comment Chinese Remainder Theorem - solving a modulo with big numbers
I'm stuck under a tree trunk! @Somebody please help!
Mar
21
awarded  Yearling
Dec
21
awarded  Constituent
Dec
9
awarded  Caucus
Dec
3
comment Nobody told me that self teaching could be so damaging…
I get the sense that you feel you know every aspect of the subjects you are taking. There is absolutely no way that is true; you simply haven't looked hard enough to find the interesting stuff. Often times the book will have exercises geared toward the more advanced reader at the end of its exercise sets, see if that is true for your textbooks. Also, look for patterns in your problems sets or see if there is some abstract result that solves your problems more efficiently or gives you deeper understanding of the answers.
Dec
2
comment Determine $\phi(2^{399}+1)$
My crystal ball works!
Nov
14
comment Determine $\phi(2^{399}+1)$
Intended answer: some very large number.
Oct
19
comment xy+x+y=0 What is the inverse Element?
@Clayton Your confusion arises from mixing up the two multiplication operations.
Sep
30
awarded  Explainer
Sep
24
awarded  Autobiographer
Sep
4
comment Bisectors problem
So it is just a hypothesis that N exists and B lies between M and N?
Sep
4
comment What is the flaw in this proof that all triangles are isosceles?
You read the statement somewhere, it would help us if you indicated where you read it.
Sep
3
comment Bisectors problem
That's what I guessed, chen h.; however consider a 45-45-90 triangle with legs AC, BC. Then the bisector of the supplementary angle of ACB is parallel to AB.
Sep
3
comment Bisectors problem
Just wondering, what is the supplementary angle of a given angle? I took a guess, but it does not always happen that B lies between M and N with my choice.
Sep
1
comment Right-adjoint to the inverse image functor
I discovered the right-adjoint $g$ by considering two simple examples. Let $f_1$ be the function from the set of two points to the singleton set. Let $f_2$ be the function $\{a,b,c\}\to\{u,v\}\colon a,b\mapsto u,c\mapsto v$. Perhaps these considerations will help you too.
Sep
1
comment question about $Spec(A)$ in Atiyah's book Introduction to Commutative Algebra
@claire Yep, there is no such thing as an infinite sum. We sometimes abuse notation and write $\sum_{i\in I}f_ig_i$, $g_i\in A$ and all but finitely many of the $g_i$ are zero.