equation = @(x,y) y + diff(y, 2);
domain = [0 10*pi];
conditions = @(y) {y(0) - 1; diff(y,10*pi)};
options = tau.settings('degree', 100, 'pieces', 5);
problem = tau.problem(equation, domain, conditions, options);
% solution via tau method
[yn, info] = tau.solve(problem);
% compare result with the exact solution
u = linspace(yn);
semilogy(u, abs(yn(u)-cos(u)));
title('Absolute error')
