1.

For any sets A, B and C prove that:A × (B ∩ C) = (A × B) ∩ (A × C)

Answer»

Given: A, B and C three sets are given. 

Need to prove: A × (B ∩ C) = (A × B) ∩ (A × C) 

Let us consider, (x, y)∈A × (B ∩ C) 

⇒ x∈A and y∈(B ∩ C) 

⇒ x∈A and (y∈B and y∈C) 

⇒ (x∈A and y∈B) and (x∈A and y∈C)

⇒ (x, y)∈(A × B) and (x, y)∈(A × C) 

⇒ (x, y)∈(A × B) ∩ (A × C) 

From this we can conclude that, 

⇒ A × (B ∩ C) ⊆ (A × B) ∩ (A × C) ..... (1) 

Let us consider again, (a, b)∈(A × B) ∩ (A × C) 

⇒ (a, b)∈(A × B) and (a, b)∈(A × C) 

⇒ (a∈A and b∈B) and (a∈A and b∈C) 

⇒ a∈A and (b∈B and b∈C) 

⇒ a∈A and b∈(B ∩ C) 

⇒ (a, b)∈A × (B ∩ C) 

From this, we can conclude that, 

⇒ (A × B) ∩ (A × C) ⊆ A × (B ∩ C) .... (2) 

Now by the definition of the set we can say that, from (1) and (2), 

A × (B ∩ C) = (A × B) ∩ (A × C) [Proved]



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