If A=B prove AUB=AnB

If two sets are same let a and bthen we can say a = b

according to definition of intersection it is function that contains common enements from both setsas a=b so all elemnts are commonso a = a n bor b = a n b

in union the function has all elements of both sets and in set no element repeats so

a u b = aor a u b = b

as a u b = a or b and a n b = a or b so we can conclude here that

a u b = a n b as a = b / / defined above