The following situation can arise from a 3-3 invasion.
White has lived in the corner.
Klaus: I think I read that the following continuation is supposed to be some kind of usual exchange later. (Might be wrong though.)
In the game in question, White decided to play tenuki after , in order not to end in gote if Black decides not to play
in the upper diagram. How should Black continue?
Charles A well-known position: can become ko.
Lucas: Yes. If it is Black's turn it is ko (as shown below) and dead if Black has a stone at the circle point. Covered in a later chapter of Life And Death by JamesDavies.
If it is White's turn, she can live unconditionally by playing at b, regardless of whether Black has a stone at the circled point. By playing at a, White turns the shape into the "long L group with a leg" (to use LifeAndDeath terminology), which is alive.
Klaus: Could you please show us the ko sequence? I can't find it myself, and I don't know where to look it up. (And I guess, others might have the same problem...)
Charles You could try Go Tools. But why not try to solve the problem? Bob has provided an answer below.
At learning from Takemiya the following reduction was mentioned. White is left with barely two eyes, but can Black do better?
At Positional Judgement Problem 2 / Discussion it was suggested, that Black cam kill by playing hane underneath. But is that right? On that page, a move at a is suggested, but White seems to die after b.
Lucas: The position on that page is slightly different and Black can unconditionally kill there (colors are reversed there) but not here (as shown below).
White is a different idea.But is it enough?
(No, see below.)
Playing here can lead to the mentioned reduction, if Black continues with
at a. Other moves seem to fail.
What alternatives are there for
? Is White alive?
SnotNose: How does White respond to ?
Klaus: The "Double Hane" seems to kill, cool idea!
However, I'm still not completely convinced. I want to present an idea I found at oki wants tobi?:
Different ikken tobi
White seems to be alive here, but of course, Black kan play differently in this case. He might try the vital point, but...
... the sequence a, b, c, d won't kill White, and beginning with will be answered at a. so how is White killed?
BobMcGuigan: Here are some important sequences in this position: