# How do I find the frequency response of an ideally sampled-in-time signal?

Please consider the image below. It contains the problem and the work I have done. I am off by a minus sign and I'm not sure how to get rid of it. Consider what I have and what the book has. http://i.stack.imgur.com/FHbi0.png

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 Why don't you put it here in LaTeX? Reading text from an image is rather tedious. If you need help with LaTeX, see for example this guide. If you've never typeset a formula in TeX before, it may require a little effort, but it will certainly make people more likely to read what you mean to say, and if you're planning to ever write any mathematics you need to learn it anyway. – tomasz Nov 5 '12 at 23:11