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bio website linkedin.com/in/gt6989b
location New York, NY
age 36
visits member for 3 years, 4 months
seen 2 days ago

Jan
2
comment Finding limit by l'hospital rule.
Are you saying $A, B$ are independent of $x$? Then $A=B=0$ seems like the only possibility, but $x^3 \tan^{-1} (x)$ does not converge I believe
Jan
2
comment Probability of picked cards to be smaller than the largest picked card
@Henry likely just put it down as the first in a pile...
Jan
2
comment Probability of picked cards to be smaller than the largest picked card
What does probablistic equations mean in this context? Expected values of quantity in each pile?
Jan
2
comment Which Expression of e Converges Fastest?
... and is much quicker to compute using Hermite evaluation
Jan
2
comment Find $k$ such that the vector with $w_n=1/(1+a_n k)$ is orthogonal to a given vector
@emanuele Lots of people ask questions here without any clue as to what the definitions mean. I am glad you understand. So for each $N$ you must find roots of a polynomial of degree $N$ to get the values. E.g. no guarantees for $N=1$, and $$ -\frac{v_1+v_2}{v_1 a_2 - v_2 a_1} $$ for $N=2$. So you can possibly find more analytical solution for $N=3,4$ but no more than that.
Jan
2
comment Prove that: $\dfrac{x^2}{a^2}+\dfrac{y^2}{b^2}+\dfrac{z^2}{c^2}=1$
Thanks, Ehsan - I was wondering why it was tagged abstract-algebra...
Jan
2
comment Are the 2nd order linear differential equations vector space?
Hi, Arash, welcome to Math.SE! Using MathJax to edit your formulae would be a real help... Does this require the homework tag as well?
Jan
2
comment Do I calculate it right for the hypothesis testing?
Looks very reasonable to me.
Jan
2
comment Evaluating sign of inequality under constraint
@tomka What is more interesting is to find the entire range of values of $a$ where it is true and false...
Jan
2
comment Evaluating sign of inequality under constraint
for some real $a$? Try $a=0$ :-). Do you mean for any real $a$?
Jan
2
comment Deciding whether this integral is convergent or divergent: $\int_1^\infty \frac{e^{\sqrt {x}}}{\sqrt{x}}\,\mathrm dx$
@Pumpkin if you sub correctly your integral becomes $\int e^{-y}$...
Jan
2
comment Deciding whether this integral is convergent or divergent: $\int_1^\infty \frac{e^{\sqrt {x}}}{\sqrt{x}}\,\mathrm dx$
The last step should likely read $<x^{-1.5}$ and the integral as well, which would actually make it convergent :-) since $\int_0^\infty x^{1.5} dx = + \infty$...
Jan
2
comment detecting dynamic parts in graph
Hi, welcome to Math.SE! Thanks for your question, it looks interesting but I could not really comprehend what you are asking. Could you consider giving an example?
Dec
30
comment Delete a vertex,how to show that graph remains connected?
May help to post a definition of a coherent graph, I don't think it's commonly known. I found one here on p.10: idsia.ch/~zaffalon/papers/2009aij-cgs.pdf (Def.9).
Dec
30
comment What is the CPLX button on a calculator?
@DantheMan here is a brief summary in Russian if it helps (1okey.ru/privat/instruction/instruction/…). They do agree that CPLX means a register of complex numbers...
Dec
26
comment How to find whether Linear system has unique solution or not?
@Andy No. The 4th row has the first 3 entries of 0 and the last one is $f$. The last equation reads $0 x_1 + 0 x_2 + 0 x_3 = f$, so if $f \neq 0$, there are no solutions.
Dec
26
comment Inequality Case by Case way
@franck $x$ changes sign at 0.
Dec
26
comment A logical problem I can't solve. Please help. (About money)
Not sure what you are asking. You ate 45 worth of food and still have 1 left (total 46), for which you compensated by returning 23 to 2 people at the same time...
Dec
26
comment A logical problem I can't solve. Please help. (About money)
@Wicht retagged
Dec
26
comment Elementary number theory problem
@ErickWong Thanks, totally missed that $n \in X$.