Symbol used to denote intervals.

Square brackets are always used in pairs.

Sometimes, square brackets are used as a symbol to group operations, like this:

8 + 5[4 + 3(8 – 4) – 2 (9 – 8) + 6] – 12 = 96

### Notation

The square bracket symbol is “[ ]”.

### Examples

The interval [3, 8] indicates “{*x* ∈ \(\mathbb{R}\) ∣ 3 ≤ *x* ≤ 8}”.

The interval [3, 8[ indicates “{*x* ∈ \(\mathbb{R}\) ∣ 3 ≤ *x* < 8}”.

The interval ]3, 8] indicates “{*x* ∈ \(\mathbb{R}\) ∣ 3 < *x* ≤ 8}”.

The interval ]3, 8[ indicates “{*x* ∈ \(\mathbb{R}\) ∣ 3 < *x* < 8}”.

### Examples

The first person to use square brackets was Raphael Bombelli (1526-1573) in his text called *Algebra*. He was one of the great Italian algebrists of the 16th century. He used the four base operations with complex numbers and used continuous fractions to calculate square roots and cube roots.