Help using fzero function in matlab

  • #1
Hey guys i have nonlinear equation: dy/dt = 3siny + y - 2. I got the direction field with this

>> [T,Y] = meshgrid(-5:00.2:5, -5:0.2:5);
>> S = (3*sin(Y))+Y-2;
>> L = sqrt(1 + S.^2);
>> quiver(T, Y, 1./L, S./L, 0.5), axis tight
>> xlabel 't', ylabel 'y'
>> title 'Direction Field for dy/dt = (3*sin(Y))+Y-2'

NOw i need to use fzero function to find approximate values for all the equilibria of teh system. I just dont' know how to use fzero with a dif equation like this. ANy help is appreciated. thanks Also, i know the values are around 0.5 and 4.
 

Answers and Replies

  • #2
saltydog
Science Advisor
Homework Helper
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Pepsi24chevy said:
Hey guys i have nonlinear equation: dy/dt = 3siny + y - 2. I got the direction field with this

>> [T,Y] = meshgrid(-5:00.2:5, -5:0.2:5);
>> S = (3*sin(Y))+Y-2;
>> L = sqrt(1 + S.^2);
>> quiver(T, Y, 1./L, S./L, 0.5), axis tight
>> xlabel 't', ylabel 'y'
>> title 'Direction Field for dy/dt = (3*sin(Y))+Y-2'

NOw i need to use fzero function to find approximate values for all the equilibria of teh system. I just dont' know how to use fzero with a dif equation like this. ANy help is appreciated. thanks Also, i know the values are around 0.5 and 4.
The equilibrium points for an autonomous DE are the values of y such that the RHS=0. If I plot the RHS as a function of y, I get 3 zeros. I use Mathematica so can't help with matlab. Doesn't it have a help function? You know, place the cursor on the function then press the F1 key. Surely you can just treat it (RHS) as an algebraic equation in y and solve for the roots right?
 

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