Hacker Newsnew | past | comments | ask | show | jobs | submit | srean's commentslogin

A related interesting fact is that small angular motions compose almost like vectors, order does not matter (i.e. they are commutative). This makes differential kinematics easier to deal with when dealing with polar or cylindrical coordinate systems.

Large angular deflections while being linear transforms, do not in general commute.

It will spoil the linear relation in your elegant expression, but a slightly better approximation for cos for small θ is

    1 - 0.5θ²

A notable approximation of ~650 AD vintage, by Bhaskara is

   ArcCos(x)= Π √((1-x)/(4+x)).
The search for better and better approximations led Indian mathematicians to independently develop branches of differential and integral calculus.

This tradition came to its own as Madhava school of mathematics from Kerala. https://en.wikipedia.org/wiki/Kerala_school_of_astronomy_and...

Note the approximation is for 0 < x < 1. For the range [-1, 0] Bhaskara used symmetry.

If I remember correctly, Aryabhatta had derived a rational approximation about a hundred years before this.

EDIT https://doi.org/10.4169/math.mag.84.2.098


I think HN might need a downvote button for stories if this continues.

We have "flag." Flag 'em.

I know, but that might be too harsh.

It requires very few flags to kill a story. My unstated assumption is that it will require wider participation and agreement for downvotes to do the same


Yes.

Very few painkillers that are not blood thinners. Paracetamol and canabinoids are a couple of rare exceptions.

My uncle broke his hip in his old age. He died shortly after because of the bleeding induced by painkillers.



How resistant are these drones to electronic countermeasures ?

GPS denial is a mixed bag. After about two years of efforts and counter-efforts, the Russians seemingly managed to build GPS receivers that are pretty resistant to jamming.

> That tracks. The defense primes have zero incentive to make things cheaper

Same in medical imaging industry.


Well, there are cheap portable ultrasound scanners and endoscopes.

True.

I was talking about those that are meant for hospitals. Was peripherally involved with a fledgling startup that was developing something cheap. Hospitals straightaway said noway.


They would be desirable in places with poor advanced imaging penetration like Brazil. Usually only the largest city in a state has this sort of imaging.

Strike a light in front of a parked but otherwise active fin guided heat-seeker and its freaky to watch it come alive like a lazy beagle eyeing a treat.

Is there a video of that on YT?


They are using white phosphorus on populated areas in South Lebanon. That's as vile as one can get.

Be that as it may, carpet bombing has a specific meaning, and it's not bombing one's not on board with.

In the context of Iran I agree with you.

Not so sure about South Lebanon. From whatever media coverage I saw, some look not that different from carpet bombing.


Evidence for the claim?

Human Rights Watch claim it, and have analysed photographs put on social media

https://www.hrw.org/news/2026/03/09/lebanon-israel-unlawfull...

(they have also previously documented that Israel has done this in the past)



Indeed, Israel and the US are quite vile. I have said so many times on placard which have then been ripped apart by the Israeli police. I only made a comment about the term "carpet bombing", as that is a specific term which means something else than "wide-scale bombing".

I always loved the "white phosphorous" stuff. The meme appeared on reddit out of nowhere, and once it did it made everyone who heard it completely utterly stupid. Suddenly it's a chemical weapon, the worst sort of atrocity anyone's heard of.

The meme will never die. Skynet could be hunting down the last of humanity hiding in caves, and those humans will be crying "maybe it will just be nukes, please god, don't let the robots white phosphorous us!".


I have handled this stuff (from remnants of unexploded munitions) and I know what it is.

It is not spectacular but it is vile and terrifying. No amount of your "rape, oh that's just surprise sex" will diminish what it is.


Reasonable people know to take your flippant tone for the colorful warning of a rotten, toxic brain.

A pinhead side pellet on his body would shut him up pretty quick.

Well, not, it would be screams of agony.


If these reasonable people knew that, then why did you have to say this? It's the dog whistle that they need so that they'll behave as expected...

White phosphorous is a way to light up the night sky during warfare. Like all warfare, it is dangerous to human life even when that's not it's direct intent... people fall off cliffs and shit while fighting (or running from it). Their deaths are no less tragic for it.

But when crackpots start screaming "they're trying to make people stampede off cliffs to their deaths!", it shows you for the very unreasonable and quite likely mentally ill person that you are.


> White phosphorous is a way to light up the night sky during warfare

Lol No. Hilariously no. The thing to use to light up night sky is Magnesium (mostly, also aluminum. nowadays specialized resins). The primary use of WP is for smoke, but it is used illegally as an incendiary munition.

For someone who talks so much about WP I did not expect this level of ignorance. Empty vessels sounds much, I suppose.

Use of WP is banned * in warfare by international treaty, on the grounds of avoiding unnecessary cruelty and suffering. There are other banned weapons, for example, dumdum bullets. *There is a specific exception made for WP, which the Israeli army habitually and illegally abuses.

No other army is known to be a repeat offender with regards to WP. It's use in an area with civilian population is strictly prohibited. Cliffs are not.

Given the number of false equivalences you have been drawing you sound like a shill.


I'm informing you.

That is an interesting link.

Does gmail use a special codec for storing emails ?


The biggest savings for a service like GMail are going to be based around deduplication - e.g. if you can recognize that a newsletter went out to a thousand subscribers and store those all as deltas from a "canonical" copy - congratulations, that's >1000:1 compression, better than you could achieve with any general-purpose compression. Similarly, if you can recognize that an email is an Amazon shipping confirmation or a Facebook message notification or some other commonly repeated "form letter", you can achieve huge savings by factoring out all the common elements in them, like images or stylesheets.

I kind of doubt they would do this to be honest. Every near-copy of a message is going to have small differences in at least the envelope (not sure if encoding differences are also possible depending on the server), and possibly going to be under different guarantees or jurisdictions. And it would just take one mistake to screw things up and leak data from one person to another. All for saving a few gigabytes over an account's lifetime. Doesn't really seem worth it, does it?

That's why a base and a delta. Whereas PP was talking about general compression algorithm, my question was different.

In line with the original comment, I was asking about specialized "codecs" for gmail.

Humans do not read the same email many times. That makes it a good target for compression. I believe machines do read the same email many times, but that could be architected around.


Yes.

These and other email specific redundancies ought to be covered by any specialized compression scheme. Also note, a lot of standard compression is deduplication. Fundamentally they are not that different.

Given that one needs to support deletes, this will end up looking like a garbage collected deduplication file system.


Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: