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

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.

Answer 1

[Seth DeLand]

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)