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 February 17th, 2011, 05:32 PM #1 Newbie   Joined: Feb 2011 Posts: 15 Thanks: 0 Trig Identities I am studying for my DSP midterm, and I am stuck on some trig identities. I have this sample question: If the difference equation is y(n)=x(n) + x(n- , and x(n)=cos(wn)*u(n), and w is equal to 2pi, and u(n) is the unit step, and n=8, express the answer in the form y(n)=A(cos(wn + B)). I have... y( =cos(w +cos(8w)^2 + sin(8w)^2 y( =cos(8w)+1 .... How can I simplify that further? February 19th, 2011, 02:25 PM   #2
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Re: Trig Identities

Hello Natalie,

Quote:
 Originally Posted by You y( =cos(8w)+1 .... How can I simplify that further?
The range of A(cos(w8 + B)) is [-A,A].
The range of cos(8w)+1 is [0,2]

-A=0 would imply A=0, but A=2 implies well, A=2. Contradiction, therefore,

You cannot write y( =cos(8w)+1 of the form y(n)=A(cos(wn + B)):=A(cos(w8 + B)). February 28th, 2011, 09:00 AM #3 Newbie   Joined: Feb 2011 Posts: 15 Thanks: 0 Re: Trig Identities Alright that makes sense as to why I cannot do that, but I still don't understand how to get it to that form. Tags identities, trig Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post mathatesme Trigonometry 3 January 13th, 2014 04:20 AM taylor_1989_2012 Trigonometry 4 March 4th, 2013 02:05 AM Gokias Trigonometry 10 July 13th, 2011 02:14 PM jordanshaw Algebra 1 October 15th, 2010 11:47 PM jordanshaw Algebra 4 October 15th, 2010 01:28 PM

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