dplanet
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 Apr 7 comment Given a random sequence give a recurrence defining it. Might this be possible with some application of interpolants? Nov 25 comment Electric dipole potential (Taylor expansion) thank you for all your help, cleared it up a lot! 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. Mar 7 comment Continuity with normed spaces Why can we assume that $\delta \le 1$? Mar 7 comment Continuity with normed spaces My apologies, I've fixed that (the $f+g$ was from the previous question in the book). Feb 29 comment Cauchy sequence Oh, that rings a bell, I remember reading that a coefficient doesn't matter and we like to have just $\epsilon$ "for cosmetic reasons". Thanks. Feb 29 comment Complete normed spaces Why can you say that $||x-y||\le \frac{1}{c_{1}}$? Feb 29 comment Sum of Cauchy sequences I tried the triangle inequality, how're you supposed to go backwards with it to get it into the form desired?