Gokyo Shumyo, Section 1, Problem 11 / Solution

Black to live  

The 1-2 point prevails over the 2-2 point again.

Black to live  

There is no way White can attack Black. The distance between and is wide enough for him to make a second eye (the circled point).

Alternative life  

here also lives.

White sente  

- is a two-point sente play. - is 1 2/3 points in sente.

Wrong  

If Black carelessly plays at the 2-2 point, White takes the vital point with and sets up an approach ko. Black can't block at a because of shortage of liberties. So he has to fight the ko at . After White recaptures the ko ...

Wrong (cont.)  

... she connects at , putting the four black stones in atari. Black takes the ko with putting three white stones in atari; White connects at , and Black makes an eye with . Now White takes the ko.

So, White has to play an extra move, and if Black loses the corner, he will have played twice elsewhere in return.

Anyway, living unconditionally is much better for Black.

Wrong (ii)  

Enlarging the eyespace with is dubious. After , Black has to defend his cutting point with . Further enlarging the eyespace with forces and now White can either play atari at a in the future, or if Black plays there, almost fill Black with a farmer's hat by playing at b.

Anonymous: Isn't Black at a death in gote? W has made it impossible to DivideTheSpace already.

unkx80: Yes. But "almost fill" does not mean that you must play there immediately.

Wrong (ii) (cont)  

Fancy play at doesn't help much. After on the 2-1 point, White can answer with , preventing any escape. Black has only one eye. Now and are miai points.

Wrong (ii) (cont)  

Black does better to try to run with , eliciting . Now sets up a ko.

Wrong (iii)  

leads to a throw-in ko.