Lacek
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 Feb 17 answered Damped Harmonic Oscillator Feb 17 comment $\frac{d^2}{dx^2} = \lim_{\delta x\to 0} [f(x-\delta x) - 2f(x) + f(x+\delta x))/\delta x^2]$ find a matrix It is simplest, but this is known as "second order difference scheme". If you consider numerically say an eigenproblem of finding a lowest eigenvalue, then you estimate of a lowest eigenvalue converges to the right value as $1/n^2$ with the scheme above it converges as $1/n^4$. So in short: to get "equally good" approximations it is often sufficient to use less grid points in the five-point stencil than in the (-1 2 -1) scheme. Feb 17 answered $\frac{d^2}{dx^2} = \lim_{\delta x\to 0} [f(x-\delta x) - 2f(x) + f(x+\delta x))/\delta x^2]$ find a matrix Sep 2 answered Solving for a single variable in a quadratic system Dec 19 answered Can you quantify a pattern as being “more random” Dec 19 awarded Teacher Dec 19 answered A problem For the boundary value problem, $y''+\lambda y=0$, $y(-π)=y(π)$ , $y’(-π)=y’(π)$