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Dec
2
comment (approximately) compute absolute largest eigenvalue of symmetrix 3x3 matrix
@PVAL defined "many". Definitely many more than 20.
Dec
2
comment (approximately) compute absolute largest eigenvalue of symmetrix 3x3 matrix
I'm only interested in $3\times3$ matrices (as stated). Solving for all 3 eigenvalues can be done using the exact formula for the roots of a 3rd order polynomial, but does call $\arccos$ once and $\cos$ twice, which are computationally expensive.
Dec
2
revised (approximately) compute absolute largest eigenvalue of symmetrix 3x3 matrix
specified the meaning of "many"
Dec
2
asked (approximately) compute absolute largest eigenvalue of symmetrix 3x3 matrix
Mar
15
comment Evaluate the line integral of $\frac{1}{z-a}$ over $\gamma$, where $\gamma=a+Re^{it}$, $0\leq t\leq 2\pi$ and a is a complex number
A proof was not asked for ...
Mar
14
comment Pi Day question
This is all wrong any way, as it's not 3/14/15: it makes not sense (in this mathematical context) to list month/day/year/hour. You have to be consistent and order the sub-units. Then we get 2015/03/15/09.26.53 etc.
Mar
14
revised If $\tan\alpha,\, \tan\beta,\,\tan\gamma$ are roots of $au^ 3 +(2a-x)u+ y=0$
use $\tan$ instead of $tan$
Mar
14
suggested approved edit on If $\tan\alpha,\, \tan\beta,\,\tan\gamma$ are roots of $au^ 3 +(2a-x)u+ y=0$
Mar
14
comment Evaluate the line integral of $\frac{1}{z-a}$ over $\gamma$, where $\gamma=a+Re^{it}$, $0\leq t\leq 2\pi$ and a is a complex number
Hint? answer!
Mar
14
comment Finding extrema of function of two unit vectors
@Demosthene yes, of course. so what?
Mar
14
comment Finding extrema of function of two unit vectors
@Demosthene $\hat{\boldsymbol{x}}$ is one of the function arguments and not a constant unit vector.
Mar
14
asked Finding extrema of function of two unit vectors
Sep
30
awarded  Scholar
Sep
30
accepted General solution to first-order ODE in 3D
Sep
29
comment General solution to first-order ODE in 3D
thanks. So I learned about the matrix exponential. Great! (I would accept this comment morphed into an answer ...)
Sep
28
asked General solution to first-order ODE in 3D
Sep
24
awarded  Autobiographer
Sep
3
comment Analyze rotation of satellite orbit due to transverse acceleration.
I've answered this question here.
Jun
29
comment integral of spherical harmonics over cube
I wanted to know the multipole moments of constant density cube. So knowing which vanish is only part of the story. I also need the value for those which don't. Preferrably not the numerical value, but a closed formula.
Feb
4
comment Wanted: simple invertible function with specified derivative properties
@copper.hat Sorry, that fails: $F''(0)\neq0$.