Symmetric difference of two sets

Symmetric difference of two sets

1) Meaning:-

 

A Δ B = (AUB) - (A∩ B) 

because  in the venn diagram we can see that AUB is the entire A and B circle and from that if we remove A∩B( ∝,β part) , we get only A and only B which is AΔ B

2) Number of elements in AᅀB and a question to support that:

Also n(AΔB) = n(A) + n(B) - 2n(A⋂B)

This formula is also important.

3) Question: