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 Yearling
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Mar
23
comment Factoring derivatives
It is the product rule.
Mar
10
answered Find the matrix given the determinant
Mar
2
comment Integrating a step function using antiderivatives
$F(x)$ is not continuous. It should be piece-wise continuous.
Feb
27
answered How can one intuit complex numbers from quaternions?
Feb
25
comment Transformations between coordinate frames
Your transformations dont look right. In your notation $T_{AB}, is that from A to B or the other way around.
Feb
23
comment Transformations between coordinate frames
Luigi, they are Homogeneous coordinats.
Feb
22
comment Derivative of angle between two vectors singularity!
I think that you might be running into trouble with your assumption that A and B are unit vectors. By that assumption you cannot arbitrarily change one of the vectors. It has to remain on the unit circle. Thus $\bf \dot{\hat A}\dot \bf \hat B$ and $\bf {\hat A}\dot \bf \dot{\hat B}$ are both zero. So you have a situation where you have $0/0$ and you would have to use L'Hopital's rule to solve it. I recommend that you solve for the general case.
Feb
22
answered Solving a transformation equation involving vectors and quaternions
Feb
22
comment Solving a transformation equation involving vectors and quaternions
Because quaternions are not commutative, you cannot divide. You have to pre or post multiply to manipulate both sides of the equation.
Feb
22
revised Confused with the notation/halfway done and need a little help
put in $$
Feb
16
comment Quick question about ln(0)
You know about L'Hôpital's rule right? Just put the indeterminate form into $\infty/\infty$ form as follows $x \ln x = \frac{\ln x}{1/x}$. Then take derivatives. It is pretty straight forward.
Feb
16
comment Quick question about ln(0)
You could also side step the indeterminate form by solving the equivalent integral down the $y$ axis. $\int_{0}^{1}\ln x\,\mathrm dx=\int_{-\infty}^{0}e^y\,\mathrm dy = -1$
Feb
8
comment compare lines and recognize similar ones
I think that instead of convolution you meant correlation. Convolution reverses one signal in time which would not yield the desired result. Correlation on the other hand does not reverse time and therefore would be more applicable.
Jan
31
revised How to check if a matrix is positive definite
added 1 character in body
Jan
5
reviewed Approve Show there is a path in X $\times$ Y if and only if there is a path in X and a path in Y
Jan
5
reviewed Approve Find least possible number of factors
Dec
14
awarded  Yearling
Nov
21
comment Proof with Positive Symmetric Matrices
Just work it out by the definition of SPD $x^TKx > 0, \forall x \in \mathbb R^n$.
Nov
15
comment Matrix Differential Equation with a Skew-Symmetric Matrix
Please provide an example
Sep
11
comment Why does $x^{(1/\ln(x))} = e$?
Take the natural log of both sides and insight is not far off.