value search using functions

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harley
harley on 21 Aug 2013
how do i use the fzero function or any other MATLAB function to find/verify the value of 'a', like i have done using the cubic spline method. (i am pretending that i don't know what that value is)
a=5;
w=-a:a/1000:a;
F=2*sin(a*w)./w;
%
%
w_int=-5:0.01:5;
F_int=spline(w,F,w_int);
plot(w_int,F_int,'o');
plot(w,F, '--', w_int,F_int,'o')
c = max(F_int);
[~, idx] = min(abs(w_int - 0.005));
d = w_int(idx);
a1 = (c*d)/(2*sin(d));

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Accepted Answer

Walter Roberson
Walter Roberson on 21 Aug 2013
You cannot do that. fzero() is based upon the assumption that when upper and lower bounds are provided, that they are constant, not values that vary according to the current "x" value. (Your "w" varies from -a to +a rather than being fixed.)

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