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I hate it when people bump ancient posts and make me fix it .. only to leave a downvote along the way .. -_-

@TedShifrin differentiating $f(x + t\nu)$ for a direction $\nu$ .. etc

@RandomVariable ya .. just dropping by :) Happy New Year btw! :))

@TedShifrin but we do prove all that using chain rule and FTC/by parts at the end of the day right?

we just call everything integration by parts .. Green's/Stokes all of it ..

@leslietownes loll

@RandomVariable YO!

@leslietownes 'pde-infected' XD ..

ugh .. cringes at 'good'

@robjohn I see .. thanks!! will look more into it now

@robjohn the alignment business seems the trickiest .. they sort of skedaddle around that part

@TedShifrin what can I say .. can't be nice all the time XD

@TedShifrin these are still tolerable in some sense .. sometimes I had to redo nasty calculations to answer some of the 'how did you get this/that step' .. XD

@leslietownes XD LOL

@robjohn I looked at a few youtube tutorials .. seems like fun :)

@robjohn I see .. didn't know the mirrors can be made without precision tools

@robjohn make my own? :o .. I have seen a few 'assemble yourself' models .. I wouldn't know where to find the parts individually

@robjohn I can guess by the price of some of the decent telescopes alone .. they are expensive!

@Koro I could get a good telescope for that price here :)

Happy New Year Prof @Ted

lul .. I'm in a math institute .. no telescopes around here

@robjohn I have been wanting to buy a telescope of sorts for a few years now .. but like most grad students I'm broke .. XD

@robjohn Happy New Year! :) lovely space photos!

@TedShifrin G'morning professor :)

I see ..

@robjohn I have a copy .. :) I just checked.. thanks! The article I was looking at is this one ..

Unfortunately I don't see an applet in any of my browsers

@robjohn Cool!!

Thanks!!

@robjohn Many thanks!!! is that the Harmonic analysis book?

I didn't know Besicovitch covering could be seen as a consequence of Euclidean Sphere packing :o :o ..

@TedShifrin Hello Professor! :)

@robjohn I see :-)

@robjohn I see the mean square is back!!

@robjohn It looks more like a mean square with a heart ;)

@robjohn it's not a mean square anymore ,.. :P

@Robjohn special avatar for this week?! XD

@robjohn cool!! :)

@robjohn I am okay :) How are you doing? :-)

@robjohn is that the grinch?

@robjohn what kind of virus is that blue mask supposed to keep away? XD

@skullpatrol LOL XD

@RealDumbfoggybrain and texting at the same time? ..

@robjohn there's a recent conversation thing I found ..

@robjohn ah .. I forgot we can look up the last time someone talked in chat .. or wait .. can we?

@robjohn shit! .. I thought I could act like a regular .. and get away with it

waves @robjohn :) Haven't seen you in the chat in a while!

@JingeonAn yes .. but Li's book has more modern proofs of stuff .. while covering more basic things

@BalarkaSen mostly typos .. nothing that's life threatening :P

yes :) .. get the older edition though. The newer reprint is riddled with mistakes :P