What are these symbols? - Numberphile

Let's talk about some examples of sets that are very common in mathematics, now keep in mind that with any notation like the letter that spells a is a has a different name or even maybe a different meaning in different languages, these two can be used interchangeably. a non-standard way in different fields of mathematics, but that's how they're used in most cases, that's how they're used anyway, yeah. Well, not really, this is called Blackboard Bal font. I suppose it was used to indicate a letter BAL on a blackboard where it is a little more difficult, although you can break a piece of chalk and put it on its side, but

what

ever.

I can do it with a pen though, so it's good that we have this, yeah, so this is just a bold face, which is normally the set of natural numbers, non-negative correct integers, now um, I think I said it last Now, those discussion points about whether or not zero is a natural number, let's leave it there, um, but in some context. it's easier to skip it. Next we have this Blackboard Z or Zed depending on where you are in the world and this is the set of integers, so it would be zero and one and negative one and two and negative two and so on in both directions, so these are all the integers, next we have q again Blackboard Bolt, which are the rational numbers, so these are ratios of integers, so this is one that is 1/times 1 and 1/2 and 3 9.

Okay, It's 1/3, but yes, the same. okay, or seven halves, which are also known as three and a half, okay, yes, but not the square root of two, but not the square root of two. To understand it, let's go to the real numbers, which is the front of Blackboard with r, so these are the real ones. numbers and these include things like pi and E and the square root of two and many other numbers and one number they do not include is I, which is the imaginary unit the square root of negative one or the square root of negative one to have you go a C again black bold bold

what

are your complex numbers do you have here some letters in Hebrew oh yes uh we use a lot of Alf Beth also has a prescribed meaning giml and dad not much uh but to talk about this we need to make another completely different video, Alf in will actually feature heavily in another completely different video with ASF coming very soon.

This is absolute Infinity, so stay tuned or subscribe for that. Also check out the links in the video description for more video podcasts. and links related to this work Al one is the size of how many types you can get by arranging the natural numbers well, but it's not all the different ways you can rearrange them, no is no, it's actually two for the AL knot.