DefinitionA (real) interval is a set of real numbers that contains all real numbers lying between any two numbers of the set.구간(interval)을 parentheses와 square bracket을 이용하여 표현하는 것을 꼭 기억할 것.종류An open interval (개구간) does not include its endpoints, and is indicated with parentheses.For example,$(0,1)$ means greater than $0$ and less than $1$.This means $(0,1) = \{x | 0 A closed interval (폐구간) is an..