*a*and

*b*be real numbers. We write

*[a,b] = {x *in **R** : *a <= x <= b}*.

This is a closed interval of the real line.
It contains as a subset the open interval
*(a,b)*.

See all of closed interval, no other writeups in this node.

Let *a* and *b* be real numbers. We write

*[a,b] = {x *in **R** : *a <= x <= b}*.

This is a closed interval of the real line.
It contains as a subset the open interval
*(a,b)*.