Missing solution for exponential equation

10012018, 11:45 PM
(This post was last modified: 10012018 11:51 PM by rushfan.)
Post: #1




Missing solution for exponential equation
The peak response of an underdamped second order system is:
Mpt = 1 + e^((z*pi)/sqrt(1z^2)) Where Mpt is real. For Mpt = 5, the command: solve( 5 = 1 + e^((z*pi)/sqrt(1z^2)) ,z) Returns: Which is only the negative result. The same happens in the Solve app, I only get the negative result. The same code in matlab: clc; syms z; eqn = 5 == 1+ exp((z*pi)/sqrt(1z^2)); vpa(solve(eqn,z)) produces: ans = 0.40371275194342068038575605143555 0.40371275194342068038575605143555 

10022018, 01:02 AM
Post: #2




RE: Missing solution for exponential equation
Try both answers from matlab in your expression. :)
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10022018, 03:02 AM
Post: #3




RE: Missing solution for exponential equation
What is inside e^(...) must be positive, so (z*pi)/sqrt(1z^2) > 0, this imply z < 0
Matlab positive z is a mistake. (Probably just return solved quadratic roots) 

10022018, 05:36 AM
Post: #4




RE: Missing solution for exponential equation
Xcas 1, Matlab 0 :)


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