Question #2136e

1 Answer
Oct 20, 2016

Answer:

Closed interval: specified end points are included.
Open interval: specified end points are not included.
Half-open = half-closed interval: one of the specified end point is included but not the other.

Explanation:

An interval is identified by specifying the end point values of the interval.

It may be written (for example) as something like:
#color(white)("XXX") x in [4,7]#
This is an example of a closed interval which indicates that #x# could be #4#, or any value between #4# and #7#, or #7#.

As an alternative we might have:
#color(white)("XXX")x in (4,7)#
which is an open interval which indicates that #x# could be any value between #4# and #7# but not #4# or #7#.

A half-open interval might look like
#color(white)("XXX")x in (4,7]#
...any value greater than but not equal to #4# up to and including #7#
or
#color(white)("XXX")x in [4,7)#
...which would include #4# but exclude #7#