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May
12
comment Sum of distances for vertices lying on a circle
Ahlfors's Complex Analysis, Exercise 3, page 80.
May
12
revised Is Lipschitz's condition necessary for existence of unique solution of an I.V.P.?
edited body
May
12
comment Is Lipschitz's condition necessary for existence of unique solution of an I.V.P.?
To your first question: that problem, for $x\in[0,1]$ that problem is equivalent to two IVP. To your second question there's a typo I'm about to correct.
May
10
revised Is Lipschitz's condition necessary for existence of unique solution of an I.V.P.?
added 426 characters in body
May
10
answered Is Lipschitz's condition necessary for existence of unique solution of an I.V.P.?
May
4
revised Compute $\lim\limits_{n\to \infty}\frac{\prod\limits_{k=1}^{n}a_k}{2^n}$
Formatting
Apr
27
comment Consider the equation: $x' = f(t,x)$. Prove that there is a two-way correspondence between the initial and the limits of the solutions.
It doesn't matter. There's no problem in posting the original problem in portuguese. Which limits and which initial? Initial conditions, and limits at infinity?
Apr
27
comment Consider the equation: $x' = f(t,x)$. Prove that there is a two-way correspondence between the initial and the limits of the solutions.
Hello! Can you please be more precise about what is the meaning of a "two-way correspondence between the initial and the limits of the solutions"? If you have an screenshot or a pic of the problem in its original source, it might be helpful to post it here :-)
Apr
17
comment Show that the set of isolated points of $S$ is countable
Look at Theorem 4 in here
Apr
9
revised (Edited Duplicate) Let $(x_{n_n})$ be a sequence of positive real number that has no convergent subsequence. Show lim $x_n$ = +$\infty$
deleted 2 characters in body; edited title
Mar
28
comment Basic problem about measurable sets
I misread your question
Mar
22
revised When does $az + b\bar{z} + c = 0$ represent a line?
Conditions are just enough.
Mar
21
comment Is continuous and integrable function bounded?
It's bounded almost everywhere.
Mar
21
revised Is continuous and integrable function bounded?
English
Mar
15
awarded  Yearling
Mar
12
comment Let $A^{774}=0$. Show that if $t$ is an eigenvalue of $A$, then $t=0$
Hint: minimal polynomial.
Mar
8
comment Show that a finite group with certain automorphism is abelian
Thanks to @Vignesh Manoharan for adding the source.
Mar
8
revised Show that a finite group with certain automorphism is abelian
Adding source.
Mar
3
comment Group theory, quotient groups?
Part of the question is answered here. For the rest, hint: first isomorphism theorem.
Mar
1
comment What do Algebra and Calculus mean?
@Tim I once heard that analysis is deduce things from the properties of the real numbers. That seemed accurate to me because everywhere in analysis one keep coming back to real numbers. Beautiful answer André.