Here you will learn what are subsets in math i.e. proper subsets and improper subsets with examples.
Let’s begin –
What are Subsets in Math ?
Definition : Let A and B be two sets. If every element of A is an element of B, then A is called a subset of B.
If A is a subset of B, we write A \(\subset\) B, which is read as “A is a subset of B” or “A is contained in B”.
Thus, A \(\subseteq\) B if a \(\in\) A \(\implies\) a \(\in\) B.
The symbol “\(\implies\)” stands for “implies”.
If A is a subset of B, we say that B contains A or B is a super set of A and we write B \(\supset\) A.
If A is not a subset of B, we write A \(\nsubseteq\) B.
Improper Subset
Definition : Every set is a subset of itself and the empty set is subset of every set. These two subsets are called improper subsets.
Example : Let Set A = {1, 2, 3}. Write its improper subsets.
Solution : Since every set is a subset of itself. Therefore {1, 2, 3} is subset of A and empty set (\(\phi\)) is a subset of every set.
\(\implies\) {1, 2, 3} and \(\phi\) are improper subsets of the given subset A.
Proper Subset
Definition : A subset A of a set B is called a proper subset of B if A \(\ne\) B and we write A \(\subset\) B. In such a case we also say that B is a super set of A.
Thus, if A is a proper subset of B, then there exist an element x \(\in\) B such that x \(\notin\) A.
In the example given below set B is the proper subset of set A.
Example : Let Set A = {1, 2, 3}, Set B = {1} and Set C = {1, 4}.
Then {1} \(\subseteq\) {1, 2, 3} but {1, 4} \(\nsubseteq\) {1, 2, 3}
\(\implies\) Set B is the subset of A because every element of B is in Set A. But Set C is not the subset of A because element 4 is not in Set A.
Theorems on Subsets
(i) Every set is a subset of itself.
(ii) The empty set is a subset of every set.
(iii) The total number of subsets of a finite set containing n elements is \(2^n\).
