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Solve Command for Unknown Parameters

Asked by Mostafa Salam on 23 Aug 2018
Latest activity Edited by Mostafa Salam on 23 Aug 2018
Dears,
How can I solve the following equation with MATLAB to get the value of the unknown parameter (beta):
7*exp(-0.008*beta)+0.008*sin(7*beta)-7*cos(7*beta)=0
I tried to use "SOLVE" command, but it give me every time: beta = 0
I don't know what's the incorrect in it.

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2 Answers

Answer by Steven Lord
on 23 Aug 2018
 Accepted Answer

Let's see how your function looks in a neighborhood around y = 0.
f = @(beta) 7*exp(-0.008*beta)+0.008*sin(7*beta)-7*cos(7*beta);
fplot(f);
yticks(0);
grid on
ylim([-0.5 0.5]);
beta = 0 does look like a solution, but it is not the only solution. Calling fzero with different initial guesses may allow you to calculate those other solutions. If you think about your function you should be able to calculate roughly how far apart the local minima of your function should be, and that can inform your choice of starting points for fzero.

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Answer by Walter Roberson
on 23 Aug 2018

If you vpasolve you can pass in a range to search over.

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