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location Buenos Aires, Argentina
age 21
visits member for 3 years, 9 months
seen 10 hours ago

(my about me is currently blank)


Mar
8
comment directional derivative unit vector
If you have an angle $\theta$, the unit vector in that direction is $(\cos \theta, \sin \theta)$.
Feb
29
accepted How to solve $y'' = -\frac{k}{y^2}$, with $k > 0$?
Feb
29
comment How to solve $y'' = -\frac{k}{y^2}$, with $k > 0$?
It wasn't my physics test, it was one some friends in my same year did. But never mind that, thank you for all your help.
Feb
29
comment How to solve $y'' = -\frac{k}{y^2}$, with $k > 0$?
I end up with $\int \frac{\mathrm{d}y}{\sqrt{\frac{2k}{y}+C}} = \int \mathrm{d}x$. According to WolframAlpha, the integral on the left hand side is quite complicated, and it seems impossible to solve for $y=y(x)$. Am I doing something wrong?
Feb
29
comment How to solve $y'' = -\frac{k}{y^2}$, with $k > 0$?
Well, I get $y' = \pm \sqrt{2k(\frac1{y}-\frac1{y(0)})}$ (I made it clearer in the title that the right hand side of the equation should be negative), but I don't know how to go from there.
Feb
29
revised How to solve $y'' = -\frac{k}{y^2}$, with $k > 0$?
edited title
Feb
28
comment How to solve $y'' = -\frac{k}{y^2}$, with $k > 0$?
@Henry: I know, but mathematically does it make any difference?
Feb
28
asked How to solve $y'' = -\frac{k}{y^2}$, with $k > 0$?
Feb
19
comment A basic question about integration
@Gingerjin: the limit when $x$ goes to $0$ is $\infty$, not $0$, so it doesn't make sense to define it as such. It would not be continuous.
Feb
19
comment A basic question about integration
$x^{-\frac1{2}}$ is not integrable in $[0, 1]$, because it's not defined at $x = 0$.
Feb
16
accepted Confused about characteristic equation of a linear ODE
Feb
16
comment Confused about characteristic equation of a linear ODE
I guess that makes sense. If I understand correctly the idea is that you want a real space of solutions so you try to find a base made out of real functions, right?
Feb
16
asked Confused about characteristic equation of a linear ODE
Feb
11
answered Where should the exponent be written in numbers with units of measurement?
Feb
6
accepted Am I doing this double integral right?
Feb
5
asked Am I doing this double integral right?
Feb
4
accepted How to justify this differential manipulation while integrating?
Jan
17
revised Trigonometrical functions
latexified
Jan
17
suggested suggested edit on Trigonometrical functions
Jan
8
revised Solving $\int\frac{\ln(1+e^x)}{e^x} \space dx$
Misdiagnosed the error