1. ## Maths symbol?

Hey, attached is from a maths textbook. THere's this 'R' looking symbol that i haven't seen before. What does it mean and how is it typically used.

Thanks

2. ## Re: Maths symbol?

I think that just means 'Real Numbers'.

It's mainly just used as a restriction or as some extra info to a question I think such as saying that 'x' is/can only a real number.

3. ## Re: Maths symbol?

IT means in reals, its just limiting the numbers in the real system aka not being able to take roots of imaginary

4. ## Re: Maths symbol?

As everyone else said, it's set notation for all real numbers.

Real numbers include integers, rationals and irrationals such as $e$, but stop short of including imaginary numbers like $i$.

Sometimes it will be written $x \in \mathbb{R}$, which means the same thing.

Here are some other ones that you may encounter:

$\mathbb{N}$ (natural numbers)

$\mathbb{Z}$ (integers)

$\mathbb{Q}$ (rationals)

$\mathbb{C}$ (complex numbers)

You can also add a superscripted sign to place further restrictions.

e.g. $\mathbb{Z}^+$ means positive integers.

5. ## Re: Maths symbol?

Ohhh thanks

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