I only remember useful things. And I consider these useful because I did some low level graphics programmed once and had to use them in practice. Once you understand why these things exist, it becomes that much easier.

If someone didn't learn enough trigonometry in school:

1+tan^2^c = cos^2^c/cos^2^c + sin^2^c/cos^2^c = (cos^2^c + sin^2^c)/cos^2^c = 1/cos^2^c;

sqrt(1/cos^2^c) = |sec c|

Well, on the side of easy ones there is "if the last digit is divisible by 2, whole number is divisible by 2". Also works for 5. And if you take last 2 digits, it works for 4. And the legendary "if it ends with 0, it's divisible by 10".

The divisability rule for 7 is that the difference of doubled last digit of a number and the remaining part of that number is divisible by 7.

E.g. 299'999 → 29'999 - 18 = 29'981 → 2'998 - 2 = 2'996 → 299 - 12 = 287 → 28 - 14 = 14 → 14 mod 7 = 0.

It's a very nasty divisibility rule. The one for 13 works in the same way, but instead of multiplying by 2, you multiply by 4. There are actually a couple of well-known rules for that, but these are the easiest to remember IMO.

Try MusicBrainz Picard. I've had good experience with their recognition quality.

There is no such thing as "zeroith". Does not matter which numbers you slap on the tables, the one with the lowest number will always be the first. The word "first" has nothing to do with indices, it's just an antonym for "last".

The problem is, in my opinion, that they post memes that are clerly provoking non-vegan people for discussion.

It's weird to jump under a "here are my 15 ways of cooking asparagus" post with anti-vegan content. But "look at these carnovorous clowns" memes are clearly offensive.

Some people have to use their stuff for a variety of reasons, don't be a dick about it.

They are probably just using your IP address to determine the location. That will show the location of your ISP, not your location. That's not much more info than any other server gets when you are connecting to it. Also does not require Mozilla to send any geolocation data.

It's just a domain name, it has nothing to do with sites being safe. Just as any other site, they may be malicious, may be not, depends on who runs the site.

Nah, Georgian is arcs and circles everywhere, like this: ეს ქართული დამწერლობაა.

RiF.