| 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
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