A null set, a finite set, a countable infinite set and an uncountably infinite set.
Set A is a finite set if n(A) =0 (that is, A is the empty set) or n(A) is a natural number. A set whose cardinality is not 0 or a natural number is called an infinite set.
A countable set is defined as one whose elements can be put into one-to-one correspondence with elements of the set of counting numbers or some subset of it. A countable set can be infinite: for example all even numbers. This raises the strange concept where a subset (positive even numbers) has the same cardinality as all counting numbers - which should be a set that is twice as large! Even more confusingly (perhaps) is the fact that the set of all rational numbers also has the same cardinality as the set of counting numbers. You need to go to the set of irrationals or bigger before you get to uncountable sets. So you have the weird situation in which there are more irrationals between 0 and 1 than there are rationals between from 0 and infinity (if infinity can be treated as a value)! There is a minority definition of countable which means containing a finite number of elements as opposed to uncountable meaning infinitely many elements. However, these definitions are essentially the same as the finite sets and infinite sets and so there is little point in using them.
Finite, no.
An empty set is considered a finite set because it contains zero (0) elements and zero is a finite number.
A null set, a finite set, a countable infinite set and an uncountably infinite set.
Set A is a finite set if n(A) =0 (that is, A is the empty set) or n(A) is a natural number. A set whose cardinality is not 0 or a natural number is called an infinite set.
A finite set has a finite number of elements, an infinite set has infinitely many.
It is a measure, but it isn't always sigma-finite. Take your space X = [0,1], and u = counting measure if u(E) < infinity, then E is a finite set, but there is no way to cover the uncountable set [0,1] by a countable collection of finite sets.
A countable set is defined as one whose elements can be put into one-to-one correspondence with elements of the set of counting numbers or some subset of it. A countable set can be infinite: for example all even numbers. This raises the strange concept where a subset (positive even numbers) has the same cardinality as all counting numbers - which should be a set that is twice as large! Even more confusingly (perhaps) is the fact that the set of all rational numbers also has the same cardinality as the set of counting numbers. You need to go to the set of irrationals or bigger before you get to uncountable sets. So you have the weird situation in which there are more irrationals between 0 and 1 than there are rationals between from 0 and infinity (if infinity can be treated as a value)! There is a minority definition of countable which means containing a finite number of elements as opposed to uncountable meaning infinitely many elements. However, these definitions are essentially the same as the finite sets and infinite sets and so there is little point in using them.
Yes. the set of rational numbers is a countable set which can be generated from repeatedly taking countable union, countable intersection and countable complement, etc. Therefore, it is a Borel Set.
prove that every subset of a finite set is a finite set?
Yes.
Finite, no.
In mathematics, a finite set is a set that has a finite number of elements. For example, (2,4,6,8,10) is a finite set with five elements. The number of elements of a finite set is a natural number (non-negative integer), and is called the cardinality of the set. A set that is not finite is called infinite. For example, the set of all positive integers is infinite: (1,2,3,4, . . .)
An empty set is considered a finite set because it contains zero (0) elements and zero is a finite number.
An empty set (null set) is considered finite.