Revision as of 20:21, 20 January 2011 by Xiao1 (Talk | contribs)


In question 2e

$ x(t)= \sum_{k=-\infty}^\infty \frac{1}{1+(x-7k)^2} \ $

should it be like this?

$ x(t)= \sum_{k=-\infty}^\infty \frac{1}{1+(t-7k)^2} \ $ 

yes, it should be. The correction has been made. -pm

and I was trying to find out what the peak value is for this question but turns out to be very hard to calculate the sum

$ \sum_{t=-\infty}^\infty \frac{1}{1+t^2} \ $            and wolfram said answer is π * coth(π). is there any easier way to do that? Yimin. Jan 20

You do not have to evaluate the sum. In particular, you do not need the peak value of that functions. Try to guess the period directly by looking at the sum. If you have no idea how to do this, read this page first. -pm

Yeah I'm just trying to figure out the infinite sum just for fun. Thanks.

And for question 4, are we still using the tempo? so my guess is use step functions to cut out the rhythm we want? Then put the whole line in one equation? that will become pretty messy I guess. Yimin


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Sean Hu, ECE PhD 2009