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@@ 'checkin..

btw thanks so much people for helping me :X:X:X

um... this is really dumb of me but I quite don't understand how tan^{-1}(3\ tan\frac{\pi }{2}) equals \frac{\pi }{2}

wow nice work. :D I didn't think of moving 1/2 S 4cosx / ( 5- 4cosx) dx onto the other side like what you did in step 6 of the second part of the question... My teacher told me that he got this question from last year trial @@

I tried applying the equation proven in the first part and simplified and obtained something which looked like U(0) = U(0) --> 0=0 @_@

cos nx, I've asked my teacher this question as well = =

YOu mean U(0) = 2/5 ( U(1) + U(-1) )??

I know...

the full question is : If U(n) = S (cosnx)/ (5-4cosx) dx, prove that U(n+1) + U(n-1) - (5/2)U (n) = 0. then find U (0). and I couldn't do the second part...

but you can't have tan(pi/2) can you?

Can someone please tell me if the integral S 1/ (5-4cosx) dx from x=0 to x= pi can be calculated??

in a power-consuming device, the anode is positive, and in a power-releasing device, the anode is negative.. [From wikipedia]

Those properties were proven in other experiments. This experiment (using an induction coil and a spark gap) was to prove the existence of EM waves.

I can't afford a tutor. It takes me a tremendous amount of time to learn new concepts. I use to it anyway.

but isn't that it was known, by that time, that an oscillating current could generate EM waves right?

Yes I am. I think I need someone to sit in front of me and teach me what this whole chapter is about

arrgh

I mean if he set up a circuit with oscillating current he could still generate EM waves (without sparks)

um..Is there a electromagnetic field already(in the setup)?

I'm sorry I know this is a very dumb question: Hertz produce radio wave when he made an electric spark. Why is that spark neccessary?