dplanet
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 Feb 20 awarded Popular Question Nov 15 awarded Yearling Sep 7 awarded Popular Question Jul 2 awarded Curious May 17 awarded Popular Question Apr 7 comment Given a random sequence give a recurrence defining it. Might this be possible with some application of interpolants? Mar 29 accepted Simplifying formula with Laplacians Mar 29 asked Is $\langle f \rangle$ an “inner product”? Mar 5 asked Integral of expression including partial derivatives Mar 4 asked Simplifying formula with Laplacians Feb 11 asked Calculating particle paths for a two-dimensional flow Dec 17 awarded Promoter Dec 15 asked Proof of a lower bound of the norm of an arbitrary monic polynomial Nov 25 comment Electric dipole potential (Taylor expansion) thank you for all your help, cleared it up a lot! Nov 25 accepted Electric dipole potential (Taylor expansion) Nov 25 comment Electric dipole potential (Taylor expansion) I know how to obtain the Taylor expansion of that. From your answer the lecturer neglects the $s^2$ term since $s\to 0$, then takes out a common factor or $\dfrac{e}{r}$ to get $-\dfrac{e}{r} (-1 + \dfrac{1}{\sqrt{1- \dfrac{2xs}{r}}})$. I understand how to get here, but then the lecturer rearranges this to obtain $\dfrac{e}{r}\left[ -1 + (1+\dfrac{xs}{r^2})\right]$. This bemuses me. Nov 25 comment Electric dipole potential (Taylor expansion) Ah, I see, so that's not the Taylor expansion at all. The Taylor expansion must come in the line she writes after this (sorry, was confused about this, don't see why she had to write ellipsis so presumed that was the expansion!). Please see my edit. Nov 25 revised Electric dipole potential (Taylor expansion) added 138 characters in body Nov 25 asked Electric dipole potential (Taylor expansion) Nov 23 awarded Tumbleweed