No set identity for Cartesian product?

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ainster31
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Homework Statement



Printed exercise 18: For all sets A, B, and C, A × (B ∪ C) = (A × B) ∪ (A × C).


Homework Equations



I have to use these set identities:

Theorem 6.2.2 Set Identities: commutative, associative, distributive, identity, complement and double complement laws for sets A, B, C in a universal set U, written with union, intersection and complement.


List of set identity laws numbered 7 to 12: idempotent, universal bound, De Morgan's, absorption, complements of U and empty set, and set difference, each written with symbolic equations for sets A and B.


Screenshot of a textbook box titled Theorem 6.2.3 Intersection and Union with a Subset: for any sets A and B, if A is a subset of B, then (a) A intersect B = A and (b) A union B = B.


The Attempt at a Solution



Pretty sure this is impossible because there's no identity for the Cartesian product.
 
Just go at it the old fashion way.

Suppose (a, d) [itex]\in[/itex] A X (B [itex]\cup[/itex] C). Then a [itex]\in[/itex] A. Also d [itex]\in[/itex] B or d [itex]\in[/itex] C. So (a,d) [itex]\in[/itex] (A X B) or (a,d) [itex]\in[/itex] (A X C).

Thus (a,d) [itex]\in[/itex] (A X B) [itex]\cup[/itex] (A X C).

Therefore A X (B [itex]\cup[/itex] C) [itex]\subseteq[/itex] (A X B) [itex]\cup[/itex] (A X C).

Proving the subset goes the other way follows similarly.