With only two flips, we don't need any fancy formulas . . .Ok, so say we have a magic coin.
The coin has a 30% chance to land Heads up, a 30% chance to land Tails up,
and a 40% chance to land on its Edge.
If you flip the coin twice:
(a) what is the probability that you get heads at least once?
(b) what is the probability that you get heads both times?
We have: .
(a) The opposite of "at least one Head" is "no Heads".
. . .