% compute roots using Matlab's fzero

f = @(x) cos(x) + x.^2/2 + x.^3 - 1;

x = fzero(f,0.1);

fprintf('Forward  error: %22.20e\n', abs(x));
fprintf('Backward error: %22.20e\n', abs(f(x)));


X = linspace(-1.0E-07,1.0E-07,100);
plot(X,f(X));
grid on;