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How do I find all the positive roots of (e^(-.2x ))(cos(2x))-.15x^2+1

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Rachel
Rachel on 10 Apr 2013
So far, I've done
fun=@(x) exp^(-.2*x)*cos(2*x)-.15*x^(2)+1;
x0=[-6: .1 :6];
z=fzero(fun,x0);
Nothing happens.

Answers (1)

Seth DeLand
Seth DeLand on 10 Apr 2013
2 things: 1) fzero is designed to find a single zero at a time. You will need to loop through each value for x0 and record the zero the fzero found for that starting point. Something like:
for i = 1:length(x0)
z(i) = fzero(fun, x0(i));
end
2) exp is a function that expects 1 input, if you want to calculate e^(-.2x) you can write:
exp(-.2*x)

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