Recent content by joe:)

sorry..i really can't see it at the moment...? I swear the expression for f(x) should be an infinite sum too? thanks for your patience

Thanks.. We haven't done Fourier yet.. I'm not sure how to find the expression by separation of variables..could you explain please? How will f(x) just be a constant A times sinkx? surely its an infitite sum? Confused :S Also any ideas on Q1?

Homework Statement 1)I'm analysing a standing wave formed by superposition of Asin(kx-wt) and Asin(kx+wt) so it becomes 2Asinkxcoswt It asks me to comment on the velocity of this wave. But I thought it was a standing wave - so it has no velocty in the x direction.. So what is its...

2xieir^n-1?

Ahh yes thank you.. So how do i simplify the whole thing..is it (xkxk)^n/2-1 times 2deltaij xj..but what then is the final simplified answer? Thanks.. :) I think we are nearly there? :P

i=j then it equals 1 otherwise 0? So is it (xkxk)^n/2 -1 times 6xj?? ahh i need to finish to go to bed :(

Thanks.. Is that 2(dixj)xj? What now:S?!

Thanks for your patience. So now I am just thinking about how the differentiation rules might apply here. Is it basically a product rule i.e. d/dx of x^n/2 x^n/2 so it simplifies to nei? but that's nonsensical since there needs to be two indices to convey a summation arghhhhhhhhh :( :(

Thank you.. Sorry I imagine that this is painful for you..sorry :( so i think it is eidi(xixi)^n/2 But i don't know how to simplify this? ahhhhhh :S Is there some key concept I am missing..

um xi2??

how do i apply this on the r^n now?

Ahh this helps. Thanks so del is eidi??

r=(x1i, x2j, x3k)?

so r=r'r where r' is a unit vector

Sorry..I'm not really very familiar with the eistein notation and still can't see how to do this :(