The Coding Wombat

So if L and M are lines, <L, M> is the set of all lines intersecting L and M I think

I was told it's the span

Okay quick question: If I have three lines, L,M,N, in projective P^4 space, do I have that <<L,M>,N>=<L,M,N>? It seems to make sense, but my normal intuition has not yet been of use in projective geometry

Is this room for asking questions about mathematics?

How would I know an example function that this method would work for

Yeah that was very clear, thank you

So @Christoph , do you know how that answer works out with the eigenvalues? I don't know for one how that norm is defined, the internet lists many different ones, so I'm a bit clueless

Hmm okay

@Christoph Does this ping you?

Wanna help out?

But the answer says it's empty, and I also don't understand why you calculate the eigenvalues.

I asked a question about the stability region of the two step Nyström method

Hi

The global error is always the same, for whatever method you use? Or is it always one power less than the local?

Thanks for helping

I'll read some more on wikipedia

Does the "multi-step" refer to x_2 to being based on the previous two x_i? So on multiple x_i?

My assignment is to calculate the truncation error in general (not any more specific, so I guess global). How would I calculate that? My book gives an example for the normal euler or forward euler method, but I don't know how to translate that to the central euler

I understand that this works for the local truncation error.

One more thing: In your formula for $\tau$ you use $u(x_2)$ and $u(x_0)$ and $u(x_1)$, but here the first is an exact value for every iteration right? But the second and third are approximate results from previous iterations if I'm not mistaken? (So in this case $x_0$ and $x_1$ are exact in this example, because they were given, but I mean for the next and subsequent iterations).

So, my $u_{k+1}$ in the expression in my question is an approximation for the real value corresponding to $x_2$, right? And the $u(x_2)$ is the exact value at $x_2$? If that's the case, I understand why we then subract the approximation from the exact value. I don't understand the taylor expansion of $u(x_0)$ tho, where do the minus signs come from, and how do you expand to a higher $x_i$?

Cool way of writing that difference as the definite integral of a derivative! So does this mean that the approximation error in the midpoint rule for this integral is the same as the truncation error of the "central euler method"?

And proving that <x> is also normal? q is not the smallest prime, so I guess I can't use the same proof

Okay, so what does the kernel of this homomorphism mean? What is the identity of the collection of permutations of omega?

That's okay, I'm glad I at least have some understanding of this to catch that :). Group theory is quite notation heavy and overwhelming

And K is the kernel of the homomorphism, so doesn't that mean that \phi (K) = {identy element of Sp} and that as only element?

But later on you say G/K is a subgroup of Sp, but I thought Sp was not yet proven to be a set?

So every element of G is mapped to a set in S_p by the homomorphism

So Sym(Omega) is a collection of sets with each set the elements g1H, g2H, ... gpH in a different order?

So what elements does Sym(\Omega) contain?

Okay, so Omega is the same as the set of G/H

That omega group is the same as G/H right?

Your last comment made it probably more clear, but it's very technical for me

I hope we can continue talking here.

So $S_p=G / H$? (the quotient group)

What does $S_p$ mean?

And in my case the subgroup $\langle y \rangle$ of $G$ is of index $p$ because $\frac{|G|}{|\langle y \rangle |}=p$, correct?

And sorry for not upvoting your answer, I do not have enough reputation yet.

good day/night

yes apart from a bit in the second matrix, you use 1.0, 1.0 there as width and height, while I use gui.getWidth() / 2, gui.getHeight / 2

Ok, I will, thanks. If you want you can of course post a new reply with this answer on gamedev.stack and I will make it the official answer

Ágain i'm very grateful for you taking such a lot of time to help me

yeah but not the greatest of concerns

Thanks a lot :)

But rotating around the z axis works perfectly

In the older method I also used 2 / instead of -2 /

No, I had to use modelMatrix.m11 = 2.0f / .... instead of modelMatrix.m11 = -2.0f / ....