Gokyo Shumyo, Section 5, Problem 8 / Attempts

Black to play and live by oiotoshi. The solution is a ko.  

@

Ko.  

Dieter: Two variations. a) Black plays too soon. Then White can give up the border stone and Black has too few liberties b) Black sacrifices another stone at . Then she loses the capturing race with one move.

xela: By "the border stone", you mean in the first diagram? Dieter: indeed.

Variation?  

Variation?  

Isn't it best for B to start at 1 here? That way if W connects at 2, B can atari at 3

Alive  

And if W takes the stone, something similar to the previous attempts happens.

Ko