Gokyo Shumyo, Section 1, Problem 3 / Solution

Main line  

After , which makes an eye at the circled point, a and b are miai for life.

2 and 3 are miai (i)  

After , Black has real eyes at the circled points.

2 and 3 are miai (ii)  

It seems as if creates a false eye, but the capture of three stones on the first line with results in a real eye.

2 and 3 are miai (ii continued)  

Even if White throws in at , Black lives with .

Variation  

If White captures a Black stone with , makes a second eye. Howver, if Black doesn't respond, White a kills the group.

Wrong (i)  

at the other 1-2 point is wrong. With , Black is dead. Even if Black is allowed two moves in a row, he can't live.

Wrong (ii)  

When Black plays here, White can choose between a and b to kill Black. Someone with an opinion which is the better ?

White kills at 'a'  

We must look at the ko threats black has. Here black can make two eyes by playing both 'a' and 'b', so either of them can be used as a ko threat. However, this is the only threat black can have from this position.

White kills at 'b'  

Here black will again live by having both 'a' and 'b', so they are both ko threats. Again, no more threats for black. So, are the moves equal?

White ignores threat of 'a'  

Let's say the ko was crucial enough that white had to ignore this threat. Can white have ko threats of her own to kill black again, if another big ko appears in the game? is the best she can do, threatening to make a ko for black's life at 'a'.

White ignores threat at 'b'  

Here, however, white can make a threat to kill the black group without a ko (by filling at ). 'a' is still playable, for the ko would be a hanami ko for white. Therefore, I feel that 'b' was slightly better than 'a', but the difference is really small. --Dansc

What is this diagram about? It isn't part of the immediately prior sequence. -- SGBailey

Wrong (iii)  

Connecting with Black , as shown here, is also wrong. and leave a and b as miai for the kill.

Variation  

Making the eye as large as possible, with here, seems live, but it is not the solution from the book. After , follows, and Black lives as shown.
Alternatively, if would be followed by , White a, .
is answered by .
, .
, .

Variation (2 at 1-2 point)  

If Black 1 is a mistake, then it must be because White can next play at 2. If Black now plays 3, White 4 kills the entire black group. But ...

First try  

... when Black throws in at 3, White fails.

Suggestion  

I received the following suggestion. White 2 is sente against Black 1. If Black doesn't answer ...

Main line  

4 at 1. The result is ko.

Variation 1  

takes ko.

Black lives with and , sacrificing a few stones.

Variation 2  

fills ko.

To avoid that, maybe White should start with . Now fills and is sente. This is better for White than the next diagram.

No sente  

In the Main Line solution , White's descent at is not sente.