what is the logical proof of the below formula for relation?

If I have three relations R1.R2,R3 ,then If I write the formula as
1. (R1^R2)R3 contained in (R1 R3 ^ R2^R3)
2. (R1 UNION R2) R3=R1 R3 UNION R2 R3 .

I just unable to get that why in the first case we are using contained because of intersection while in the second case we are using equals sign.

Replies

  • pratap singh, upendra
    pratap singh, upendra
    Actually both the notations: 'contained' and '=' are wrong.The correct notation: 'is equivalent to'.

    When you try to verify the above laws using Venn diagrams, you will find that the diagrams corresponding to LHS and RHS are actually the different manifestations of the same physical entity.So, there can never be anything like 'contained'. They are not 'contained', they are representing the same thing. That's it. Also linguistically, we prefer the term 'equivalent' to 'equal'.

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