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Jan
19
comment Use the Contraction Mapping Principle to show that $x=\frac19\sin\left(3x\right) + \sqrt{x}$ has exactly one solution $x\geqslant\frac{8}{9}$
As Did commented, you also need to show that $T$ maps $[8/9,\infty)$ into itself.
Jan
15
revised Proving entire function constant
added 51 characters in body
Jan
6
reviewed Approve Finding the generator of cyclic group $U(Z_{27})$
Jan
5
comment Is it possible for a manifold to have a normal vector that is zero everywhere, if so, would this indicate that the manifold is non-orientable?
Sorry, I am having a hard time understanding your question. Are you talking about a 3-dimensional manifold embedded in $R^4$? Or are you talking about a 2-dimensional manifold embedded in $R^3$? What do you mean by "a manifold to have a normal vector that is zero everywhere"? I mean, any manifold can have a vector field that is identically equal to zero, but I don't think that's what you mean.
Jan
5
awarded  Quorum
Jan
4
comment $ \mathbb Z$ is not isomorphic to any proper subring of itself.
I think it might be helpful to state the definition of "ring" used in your class / book.
Jan
4
revised How to calculate value of an analytic function in a closed disk.
added 14 characters in body; edited title
Jan
4
comment How to calculate value of an analytic function in a closed disk.
Are you familiar with the Cauchy integral formula or the Cauchy estimate? It can be shown that $|(e^f)''(0)|$ must be less than $2e$ using this method. Let me know if you aren't sure and I can elaborate.
Jan
4
revised How to calculate value of an analytic function in a closed disk.
grammar
Jan
4
reviewed Approve Integrating an exponential function
Dec
24
comment Weird isomorphisms of infinite groups
The isomorphism would be the one from $Q\oplus R/Q \to R$ composed with the isomorphism $R\to R/Q$, no?
Dec
22
comment I don't understand this notation- abelian groups
Well, the right side is well-defined. I guess it boils down to what $(\mathbb{Z}^n)_p$ means. Is it suppose to be $(\mathbb{Z}_p)^n$?
Dec
22
comment I don't understand this notation- abelian groups
Does $\mathbb{Z}p$ mean $p\mathbb{Z} = \{ pn : n \in\mathbb{Z}\}$?
Dec
19
comment Complex Analysis using derivatives
@Elliott I don't think the new link in the body of your post links to the correct article. The link provided by bourbaki works. Now, I didn't read the entire article, but that specific part with the usage of the derivative is completely wrong, which is why you might be confused by it.
Dec
15
comment Solving 2 equations (Projectile motion)
Since $\cot \theta = 1/\tan \theta$, everything cancels out nicely. You shouldn't be getting anything complicated.
Dec
15
revised Complex Analysis using derivatives
added 4 characters in body
Dec
15
comment Complex Analysis using derivatives
Why do you think $d(e^{a+bi})/da= d(e^a)/da * d(e^{bi})/da$? Are you trying to use the product rule? Also, the link appears to be dead.
Dec
15
revised Schwarz Lemma/Conformal mapping problem
This is not real analysis.
Dec
15
comment Order of $f(n) = 4n + 6n^3 - 8n^5$
How did you get $\log(n)$? Also, "order" here means what precisely?
Dec
15
comment Approximate using the central limit theorem
I'm confused... isn't the mean $60$?