What does "IR" mean in linear algebra?

Question

I am new to linear algebra and I was wondering if I could get some help for this question. I understand if it was something like this IR^2 -> IR. I have no idea what IR(=IR^1) means. Could someone please explain?

(MathJax version: $\mathbb R^2\to \mathbb R$)

Answer 1

$\mathbb{R}$, written as \mathbb{R} in MathJax, is the letter R in the special font "blackboard bold". Traditionally, several letters in this font have special meanings:

$\mathbb{R}$ real numbers
$\mathbb{Z}$ integers
$\mathbb{N}$ natural numbers
$\mathbb{Q}$ rational numbers (fractions)
$\mathbb{C}$ complex numbers