Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
implicit function solutions- help required

Subject: implicit function solutions- help required

From: Ravindra Pokharia

Date: 6 Nov, 2012 06:13:08

Message: 1 of 3

hi everyone, how do i find the solution of the following equation(i.e solution of the function ie roots/zeroes , s is my variable for which i have to find the various values).
I need it symbolically. Is it possible?
i have tried but it gives an error and that is understood- no explicit solution can be found

f(s)=(1 + s*CL*Rs)*cosh((sqrt(s*c*r))*L1) + (sqrt(s*c*r))*(CL/c + Rs/r)*sinh((sqrt(s*c*r))*L1)

can anyone help me out o this?

Subject: implicit function solutions- help required

From: Torsten

Date: 6 Nov, 2012 08:11:08

Message: 2 of 3

"Ravindra Pokharia" <ravi.ymca.vlsi@gmail.com> wrote in message <k7a9pk$lc1$1@newscl01ah.mathworks.com>...
> hi everyone, how do i find the solution of the following equation(i.e solution of the function ie roots/zeroes , s is my variable for which i have to find the various values).
> I need it symbolically. Is it possible?
> i have tried but it gives an error and that is understood- no explicit solution can be found
>
> f(s)=(1 + s*CL*Rs)*cosh((sqrt(s*c*r))*L1) + (sqrt(s*c*r))*(CL/c + Rs/r)*sinh((sqrt(s*c*r))*L1)
>
> can anyone help me out o this?

If MATLAB can not find a symbolic solution, you'll have to solve the equation numerically:
help fzero

Best wishes
Torsten.

Subject: implicit function solutions- help required

From: Roger Stafford

Date: 6 Nov, 2012 19:06:08

Message: 3 of 3

"Ravindra Pokharia" <ravi.ymca.vlsi@gmail.com> wrote in message <k7a9pk$lc1$1@newscl01ah.mathworks.com>...
> .... how do i find the solution of the following equation .....
> f(s)=(1 + s*CL*Rs)*cosh((sqrt(s*c*r))*L1) + (sqrt(s*c*r))*(CL/c + Rs/r)*sinh((sqrt(s*c*r))*L1)
- - - - - - - - -
  If your parameters satisfy L1*c/CL > 0 and L1*r/Rs > 0, there can be no real-valued solution to your implicit equation. You can see this by substituting x = L1*sqrt(s*c*r)/2, a = L1*c/CL/2, and b = L1*r/Rs/2. Then a solution to f(s) = 0 would be equivalent to solving:

 exp(x)+(x-a)/(x+a)*(x-b)/(x+b) = 0

with a > 0 and b > 0. If we first assume that L1 > 0, then x >= 0 so that exp(x) >= 1, and on the other hand abs((x-a)/(x+a)*(x-b)/(x+b)) < 1. That makes a solution impossible. A similar argument holds with L1 < 0.

Roger Stafford

Tags for this Thread

No tags are associated with this thread.

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us