Hi

Howdy, @Under

How has your day been so far?

Doing OK, and you?

Same. Just chillin'.

Well, if you have a foot of snow outside, you can really chill.

I do happen to have about a foot of snow outside, lol.

Go make a few snowpersons.

I'm not sure I have the motivation to actually be cold.

So "chillin" was a ruse.

Yeah, I'm actually pretty warm right now. Haven't even been outside today. 😅

It's my last day before classes. I'll be forced into the cold at sunrise tomorrow.

Awww ...

Yes. ;-;

@leslie will want to see evidence that you learned everything over break.

He, he...

Maybe two snowpersons would suffice.

One mini-person is the best I can do.

You can take it up with leslie and munchkin.

I'm only here for mathematics accomplishments.

@UnderMathUate Here's a calculus problem you may enjoy. What are the dimensions of the (right circular) cone of minimum volume which enclose a sphere of unit radius? Like this:

In our day, that was a 100% standard problem, @PM2. Not so much any more.

I was going to suggest it a while ago, when xander was fishing for suitable exam questions. But given the results of that exam, it probably would have stumped most of his students...

@TedShifrin Lol. Well, in that case, I think I did learn at least a few things over the break. Plus, I don't feel like I'll be rusty jumping back into things tomorrow.

Yeah, I would never have dared give that on an exam to anything but my calculus theory students, and even for them it would have been too hard. But I did assign it for homework standardly for them.

Well, I hope your proofs will be superb, @Under.

Mee tooo

For bonus points, you can also show that it's the cone of minimal (curved) surface area.

@PM2Ring I might think about that some time. We had so many problems of that nature during my calc 3 course, so after a while, I started feeling kind of "meh".

IMHO, it's a satisfying problem because there are some nice ratios involved.

This is a calc 1 question, actually, @Under, although you could certainly set it up with Lagrange multipliers.

You can do it either with geometry/algebra or with trig. One of the reasons I liked assigning it.

If you really like geometry, you can add extra circles, but that doesn't use calculus.

Lol, calc is probably the way to go.

@TedShifrin I can imagine how I might think about it geometric/algebraically, but I would have to get out my notes for an approach with Lagrange.

Lagrange just incorporates the constraints into the problem without eliminating variables.

It really makes most calc 1 problems very easy.

Eh, I guess that'll be something to try when I'm looking for something to do.

One of my colleagues at UGA actually taught his calc 1 class partial derivatives and Lagrange multipliers (without understanding the proof with the gradient, of course). In some sense, he's right that that makes things much easier on most students.

Hey, that's actually pretty cool.

We did one extra credit problem involving separation of variables in my calc (1 or 2?) course because it was honors. We never talked about differential equations again after that, so I don't really remember the process now, lol.

Not super related to what you said, but I just remembered that.

Separation of variables is actually a standard topic in calc 2.

The frick

We didn't do that in my class.

You're certainly expected to know it when you take ODE or the GRE.

Unless I'm thinking about something that is in fact "separation of variables", but I just didn't recognize it.

Solve $y' = xy$, for example. Or $y'=y^2+1$. With appropriate initial values.

Ah, ok. I recognize this now.

Write $y'=\dfrac{dy}{dx}$, manipulate that like a fraction, and write $\dfrac{dy}y = x\,dx$, for example; now antidifferentiate.

You can make sense of this formal manipulation quite directly with the chain rule.

@PM2 is having a fractal night.

I like fractals.

I played with this stuff about 15 years ago, but I recently decided to do that fractal in SVG. It took me a little while to remember how to do the small circles that are tangential to the triangles edges. :)

Alright, I'm about to go make a crappy dinner of canned soup and chicken nuggets.

Talk to you all later.

not doing any work at all. how emblematic of your vacation.

See you!

and thanks for the problem @PM2Ring

That sounds extra-high sodium and unhealthful.

@leslietownes I did do work ;-;

No worries.

'Tis incredibly high sodium and unhealthful.

i kid, of course. happy new year.

A can of soup is usually about a day's worth of sodium just by itself.

Oh for real

I don't usually look at the nutrition facts

I just know canned stuff = salt

that is a useful equation.

lol

I'm gonna make bolognese sauce a bit later, with lots of vegetables added.

I can make some green beans to go with it.

They're canned too, though.

Oh, ugh. Get them frozen instead. So much better.

(If you can't deal with fresh.)

i agree with ted.

Hell, not again.

Actually, frozen baby peas are often better than fresh, but one can't always get the babies.

Ted resigns from mathematics and will henceforth comment only on food and cooking.

Well, I can at least get frozen green beans. I don't normally get fresh stuff because I can't eat it all before it goes bad.

Yeah, I understand.

i deal with a lot of this stuff because my wife comes from a family where every vegetable is overcooked. holidays were torture. thankfully the coronavirus limited our obligations.

Well, they make up for overcooking by putting in plenty of pork fat :P

yeah. which is also nauseating.

This is why your wife became a vegetarian/vegan.

i think so

I hated brussels sprouts as a kid because my mom overcooked them (which is surprising, because my parents became pretty good cooks). I discovered when I became a cook how fabulous they are cooked properly (many options).

i had a friend in law school who insisted that i'd change my tune about brussels sprouts after i'd had her brussels sprouts. it may be possible to cook them so that they are edible but i have yet to see it.

I just checked the can and it's literally 2,140 mg of sodium...

I'm eating something else with my nuggs.

wow, that's even more than i expected.

@leslie Roast them at 450 with olive oil, salt and pepper.

How many times the daily quota is that, @Under?

@leslietownes Same, I thought it was gonna be like 300mg

Google says we should have <2,300mg per day ;-;

i think that's under the RDA. but the FDA is controlled by Big Sodium.

Even the low sodium soups are too much but taste blah. Funny how I can make soup from scratch and use very little salt in a huge pot and it's totally tasty.

Sodium chloride: the world's most popular edible mineral.

The only things I know how to cook from scratch are spaghetti and eggs

And toast.

eggs are hard. i avoid them.

What do you do with the spaghetti? Put in a jar of pre-made sauce?

Oh yeah, and toast.

@TedShifrin Yeah

That doesn't count as scratch, then.

And watch the sodium there, too!

you should learn at least one good sauce.

I should open a cooking school for math chat.

the easiest ones involve meat. much harder to do a vegetarian sauce.

I could use the help. I've probably been eating at least twice the daily amount of sodium for like a year.

I think Pedro actually has become quite a cook since he left home and went off to grad school in Ireland. Haven't seen him in forever.

sodium does mess up the palate in high quantities. i think it's possible for people to get addicted to it.

Addicted to salt? That's kind of wild.

not in the sense that they suffer or go through withdrawal. but, in the sense that it can rewire what tastes good.

if you eat a low sodium diet for six months and then open a bag of doritos, it tastes horrible.

Yeah, I assumed you meant in a similar way to how people get addicted to sugar.

How do you make stuff taste good without salt, though ;-;

When my dad was dying, his body retained too much water and he could have literally no salt. For several months, I cooked with no salt and only pepper, garlic, and lots of herbs and spices. Oh yeah, and lemon.

you do need some salt. spices can help.

unless you're ted's dad, who did not need some salt.

that's something to consider if you get married. if you don't come from a background where it's appropriate to use a salt shaker on food after it has been cooked, being around someone who thinks that is normal will drive you crazy.

Since I have heart disease and high blood pressure (on several meds, of course), I try to moderate my use of salt, but I still use it.

and vice versa.

I don't put salt shakers on the table when I have guests. They can damn well taste before politely asking for more salt.

People who just dump salt on their food without even tasting don't deserve to eat anything I cook.

my dad's second wife is a member of team salt shaker and i judge her nonstop for this. she is otherwise an OK person.

They probably don't even bother to taste anything they eat. Might as well eat at McDonalds.

she thinks it's a courtesy. "everyone can choose how much salt to add." just cook it right. salt added during cooking is very different from stuff you just shovel onto the final product.

As usual, Ted has no opinions.

I put hot sauce on everything.

Yup, it's very important to salt as you go, in layers. Not just dump it in at the end.

i waded into a morass of markvs on meta. i will decline to do so in the future.

I think that's more sophisticated than straight salt.

I avoid that person assiduously, @leslie.

But just as bad a habit, @Under. You don't taste anything you eat, I bet.

he was bothering shaun about potential copyright claims.

Oh, that's what led to my starred remark here.

I suspect there's a strong correlation between boiling the life out of vegetables and auto-condimenting (the practice of adding salt & pepper to everything before you even taste it).

PM: i agree.

It's only a copyright violation if you copy a whole chapter from a book, not paragraphs. He's an idiot.

That said, I don't appreciate it when people post my exercises from my books on here and complete solutions get posted, but that has nothing to do with copyright.

But you actually know something about copyright law, I presume.

completely bogus, and by the way there are people who do this for a living. i wouldn't wade into some discussion of theoretical physics without any background. but when legal issues are involved...

I only know stuff from being an author.

I remember that when a book was (temporarily) out of print, I had to get the author's permission to xerox the entire book for the class.

I'm sure people don't bother being proper on such things.

my copy of millman and parker is photocopied with the publisher's permission.

but yes, lots of laziness. the prevalence of laziness sometimes means that loud voices saying "uh oh, liability" are over emphasized.

I once had a xerox of Hicks's little differential geometry book, but that didn't rate keeping when I retired.

But I don't know why obnoxious, pompous ma***s has such strong feelings on this particular topic.

Why doesn't he go after all the Russian websites that upload my book and others in pdf form with zero permission ... That's totally illegal, but the publishers can't keep up with policing it.

my wife was given complete garbage advice during grad school about whether it was acceptable to employ a mathematical model created by another person for purposes of evaluating it.

the non-geographical nature of the internet makes certain kinds of enforcement effectively impossible.

Employ the model to evaluate the model? I don't follow.

There was a bit of a stir a few years ago on Physics.SE when it was discovered that someone was collecting material from there and printing it in book form. They gave proper attribution, so they weren't breaking the license conditions, but it did upset a few people that he was making money from the answers that they submitted for free.

Understandably. I'd be upset, too.

someone introduced some set of equations and things for purposes of modeling and testing some predictions. wife wanted to see if the reported results were robust and not affected by tiny perturbations. got a VERY angry email from the author telling her not to do that and hinting at unspecified consequences. moronic, baseless, borderline harassment. her department echoed these stupid concerns.

I think I helped someone on here years ago and was asked if I wanted credit in a published article. I said it was fine if he wanted to reference it like any other source. "MSE post 5/27/11" :P

i get it, if you work in the OGC of a large institution you just want everyone to not bother everyone else.

Isn't a published model/method available for people to use?

yes. for this particular example, it wouldn't even have mattered whether or not it was published, frankly.

What's the point of a published result if I can't use it with attribution?

I mean, if it's private communication and not published, then one should ask for permission.

for purposes of professional ethics yes. for legal liability, in the case i am talking about, no. but this stupid person was threatening my wife with a lawsuit, not professional scolding.

I guess it sounds like your wife's goal was to poke holes in its efficacy, so the guy got defensive?

complete idiot.

the gal, oddly enough. i understand why you assumed it would be a guy. :)

Yeah, I'm even more disappointed now to find out that was a woman treating a woman that way.

anyway i told my wife to let it go and work on something else. no need to wave a red flag in front of a bull.

I still don't understand entirely, but ... fine.

MSE actually has a cite button at the bottom of every post. Eg,

there's a joke about the lawyer who says "i'm a great attorney. i've written five wills, and every single one of them has been upheld by the supreme court." the joke is that if your wills are being contested to the point that they go to the supreme court it kind of doesn't matter if you're right or not.

Oh, interesting, @PM2. I never realized that.

We're going to have to put an asterisk on supreme court, @leslie. Before or after Tromp?

Surely if someone publishes a model it's desirable that others verify that the model behaves as advertised... unless your model is actually a pile of unsubstantiated rubbish. ;)

@PM2, it's your "unless" that I was suspecting must be the case. But that's all part of academic discourse. It's also the reason that "social science" is anything but science.

And that kind of behaviour isn't very social, either. ;)

Well, we never expected it to be!

Ted, I'm not quite sure what's going on in your avatar image, but I think it's a rotated cube. Anyway, I did a 3D interactive version. You can interact with it on a mobile or desktop browser.

sagecell.sagemath.org/…

ted: oh, for wills it would be a state supreme court. not tromp's gang.

Oh, silly me, @leslie.

@PM2 Yes, I made it as a movie on Mathematica decades ago.

Do you like my version?

Yes, it's cute. I wrote my code before Mathematica made movies so interactive. I could dig it out and update it. Probably won't.

Thanks. :)

I'm still impressed that a Web browser can do those 3D calculations so quickly. Generating the shape data is done on the server, but all the stuff involved in panning & rotating is done by JavaScript code on the client.