Interval is a representation of number set, so the representation of interval is the same as that of set. The details are as follows: (1) open interval, for example: {x | a.
(2) Closed interval, for example: {x|a≤x≤b}=[a, b]
(3) a half-open and half-closed interval, such as {x | a}
{ x | a≤x & lt； b}=[a，b]
B-a becomes the interval length.
The meaning of finite interval in mathematical geometry is as follows: line segment with finite length.
Note: suppose one
{ x | a≤x } = [a，+∞){ x | a & lt； x } = ( a，+ ∞)
{ x | x≤a } = ( -∞，a]{ x | x & lt； a } = ( -∞，a)
{ x | x∈ R } = ( -∞，+∞)
The meaning of infinite interval in mathematical geometry is as follows: a straight line. Higher mathematics includes interval analysis and interval mathematics.