Finding root of nonlinear functions

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University Glasgow
评论： Sam Chak 2022-9-8
Please, how do I find all the roots this function:
y-0.8193318913*tanh(y)+0.2931044702e-2*tanh(y)/(0.7500000000e-3*y^2-0.1622336517e-1) = 0

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采纳的回答

Torsten
Torsten 2022-9-8
Ran in:
f = @(y)(y-0.8193318913*tanh(y)).*(0.7500000000e-3*y.^2-0.1622336517e-1)+0.2931044702e-2*tanh(y);
fun = @(y)f(y)./(0.7500000000e-3*y.^2-0.1622336517e-1);
y = -6:0.01:6;
plot(y,f(y))
x0 = [-5 -4];
s(1) = fzero(f,x0);
x0 = [-1 1];
s(2) = fzero(f,x0);
x0 = [4 5];
s(3) = fzero(f,x0);
s
s = 1×3
-4.5365 0 4.5365
fun(s)
ans = 1×3
1.0e-14 * 0.4951 0 -0.4951

更多回答（1 个）

Sam Chak
Sam Chak 2022-9-8
Ran in:
Hi @University Glasgow
Read about fzero().
https://www.mathworks.com/help/optim/ug/fzero.html
The solution may look like this:
fun = @(y) y - 0.8193318913*tanh(y) + (0.2931044702e-2)*tanh(y)./(0.7500000000e-3*y.^2 - 0.1622336517e-1);
y0 = 0; % initial guess
y = fzero(fun, y0)
y = 0

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