MACM 101 Lecture 17: Lecture 17 Part 2_ Cardinality
Document Summary
Sets that are not countable are called uncountable countable sets: finite sets any subset of n. In other words we can make a list of all integers. 0, 1, -1, 2, -2, 3, -3, 4, -4, 5, -5, . The cardinality of the set of all natural numbers is denoted by 0. The set of positive rational numbers is countable. Every rational number can be represented as a fraction p/q. We do not insist that p and q do not have a common divisor. This gives an injection from q+ to n. the converse injection is f(x) = x + 1. If a is an infinite set, then | a | 0. Every real number can be represented as an infinite decimal fraction, like. Suppose we have constructed a list of all real numbers. Let bi = 4 if aii 4.