Recent content by Reid

There was no need to change the order. Now I see. :) Thanks!

If I understand you correctly, then it is allowed to change the order in the matrix multiplication? C^{-1}C^{1/2}=C^{1/2}C^{-1}

Homework Statement At the lecture yesterday the teacher just ended up with a result I could not arrive at. So, how can the below stated expression be verified? \left(C^{1/2}\right)^{T}C^{-1}C^{1/2}=I Here C is a nonsingular covariance matrix, obviously, and I is the unit matrix. I will not...

Homework Statement I cannot get my head around these equations... \dot{x}(t)=-sin y(t) \dot{y}(t)=-\frac{cos x(t)}{sin x(t)} cos y(t). They are to be solved with integration by quadratures. :S But I am not at all familiar with that technique and I can't find any tutorial for it...

Homework Statement I can not determine the solution to the diff. eq. Homework Equations \ddot{x}+k \cos{x}=0. The constant k is positive. The Attempt at a Solution I tried solving it with the methods I know and it all ended up in a big mess. I am just not used to the second...

I'm not sure if i understood this correct. Let's see, with your reasoning... I know that sigma^7=1, therefore sigma^8=sigma. Then x=sigma^4. Right?

Homework Statement x^2 = sigma. The permutation sigma = (1 2 6 7 5 3 4), a cycle of length seven. Determine x! The Attempt at a Solution I have tried a few times but my attempts are totally wrong. I don't know where to start! :S I found a similar problem in the textbook. They...

You are not too late. And those skills you are worried about not having, is something you will develop during the education. Creativity, problem solving skills... and so on! You seem to be well on your way already! Good luck! :)

At least I think I did. :) I regarded the geometrical figure with six edges. And looked at the mirroring and rotations of that structure. Is that better?

Thank you CompuChip! :)

Homework Statement I need to find a group with twelve elements that is noncommutative. Homework Equations The Attempt at a Solution I was considering a group G of the integers (-5,-4,-3,-2-,-1,0,1,2,3,4,5) with respect to subtraction. Subtraction is associative/noncommutative...

Finally, I understand! Thank you so much! :)

Sorry! I don't define the 'upper integral' at all. For me the 'Riemann integral' is defined as a limit of the Riemann sums as the norm tend to zero. That is why I am talking about the partitions and their tags. I can't find any section with upper Riemann sums either. It is only the Riemann sum.

Now, I understand. (I hope so anyway) When you wrote 'inf' I thought you meant infimum... so I thought that I was really lost since I have never heard of infimum in the context as Riemann integrals. But you must have meant int as in integral, right? And, yes! I am an analysis-rookie. ;)

Ok. :) I don't understand this!