>>937975456 (OP)well based on the way the question is asked, the answer is 1/2 because the first coin is predestined to land on heads which means it's 100% going to be heads.
>if at least 1 coin lands on heads.so under the premise at least one coin will always be heads, so the probability that both land on heads is 1/2
If the question was
>two coins are flipped at the same time, what is the probability that both coins land on headsthen the answer would be 1/4
I'll prove it mathematically
There are 2 coins with 2 faces each and 2 distinct subsets (1 and 0)
4 potential configurations
1 1
0 0
1 0
0 1
but 1 0 = 0 1
so 3 distinct configurations
BUT
based on the premise of the question one subset will always be presumed to land on heads
so the configuration becomes
1 0
or
1 1
The probability of the second coin landing on heads if one of the two is presumed to be heads is 50%