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 Author Comment/Response devil 02/05/13 2:19pm Hi, I want to calc the cutoff frequency of a System. sys = s/(1000 + s) For it I want to check were the 2. derivative of the amplitude is 0. I tried to plot every step to find the mistake. But I don't know why it don't works!? The 1. Plot is well. In the 2. and 3. nothing is plotted ... why? ampl = Abs[sys /. {s -> 2*Pi*f*I}] LogLogPlot[ampl, {f, 100, 1000}] abl1 = D[ampl, f] LogPlot[abl1, {f, 100, 1000}] abl2 = D[abl1, f] LogPlot[abl2, {f, 100, 1000}] Solve[abl2 == 0 && f > 0, f] I would be very thankful if you can help me! Thanks URL: ,

 Subject (listing for 'derivative of amplitude-frequency characteristic') Author Date Posted derivative of amplitude-frequency characteristic devil 02/05/13 2:19pm Re: derivative of amplitude-frequency character... Bill Simpson 02/05/13 6:43pm Re: Re: derivative of amplitude-frequency chara... devil 02/06/13 2:22pm Re: Re: Re: derivative of amplitude-frequency c... Bill Simpson 02/06/13 8:25pm Re: Re: Re: Re: derivative of amplitude-frequen... devil 02/07/13 1:08pm Re: derivative of amplitude-frequency character... devil 02/20/13 07:16am
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