Statistics Question

Tossing a two coins,

The sample space is,

S = { HH,HT,TH,TT}

Event A= at least one head is obtained

A= { HH,HT,TH}   ........(1)

A' = S -A = {TT}   .........(2)

n(A) = 3

And event B = both tails are obtained

B={TT} = A'       .........(3)

n(B) =1

From 1, 2 and 3,

We can say that the two events are complementary.

Hence,

Yes, event A and B are complementary events.