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Last updated at Jan. 30, 2020 by Teachoo

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Misc 9 (Introduction) Given a non-empty set X, consider the binary operation *: P(X) × P(X) → P(X) given by A * B = A ∩ B ∀ A, B in P(X) is the power set of X. Show that X is the identity element for this operation and X is the only invertible element in P(X) with respect to the operation*. Taking an example Let X = {1, 2, 3} P(X) = Power set of X = Set of all subsets of X = { 𝜙 , {1} , {2} , {3}, {1, 2} , {2, 3} , {1, 3}, {1, 2, 3} } A * X = A ∩ X = A X * A = X ∩ A = A Misc 9 Given a non-empty set X, consider the binary operation *: P(X) × P(X) → P(X) given by A * B = A ∩ B ∀ A, B in P(X) is the power set of X. Show that X is the identity element for this operation and X is the only invertible element in P(X) with respect to the operation*. Identity e is the identity of * if a * e = e * a = a A * X = A ∩ X = A X * A = X ∩ A = A So, A * X = A = X * A , for all A ∈ P (X) Thus, X is the identity element for the given binary operation *. Invertible An element a in set is invertible if, there is an element in set such that , a * b = e = b * a Here, e = X So, A * B = X = B * A i.e. A ∩ B = X This is only possible if A = B = X So, A * X = A = X * A , for all A ∈ P (X) Thus, X is the only invertible element in P(X) with respect to the given operation*.

Binary operations: Inverse

Chapter 1 Class 12 Relation and Functions

Concept wise

- Relations - Definition
- Empty and Universal Relation
- To prove relation reflexive, transitive, symmetric and equivalent
- Finding number of relations
- Function - Definition
- To prove one-one & onto (injective, surjective, bijective)
- Composite functions
- Composite functions and one-one onto
- Finding Inverse
- Inverse of function: Proof questions
- Binary Operations - Definition
- Whether binary commutative/associative or not
- Binary operations: Identity element
- Binary operations: Inverse

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.