Black is caught in a connect-and-die. If Black a, White b captures. Otherwise, White captures at a, and is connected to the outside and escapes, thus living (by tsumego convention).
The double atari is wrong here: Black chooses which group to sacrifice, preventing White from connecting and escaping. Note the the bottom row of four is good for at most one eye. After White captures (perforce: if White tries to start making an eye below, Black will capture and White only gets one eye), Black reduces that to no eyes with the double hane:
This shows that White has only the one eye.
Wauske: If white were to play 5 wouldn't it mean that, if used correctly, it would live? Meaning that black can respond at a or b white would respond at the other and that c would be followed up by d?
unkx80: Are you saying that may be answered by
? Then
can capture the
stone.
(Note: is not neccessary.)
This is the end result. Is White alive, i.e. does White have two eyes?
See also: