Beginner Exercise 19 / Solution

Sub-page of BeginnerExercise19
[Diagram]
White first to live  

Karl Knechtel: The eye at a is already secured. White needs to make one in the space around b.

[Diagram]
White first to live  

First, White chases Black around. If B2 is played elsewhere, then White will play at W2 to seal off the second eye. Similar reasoning is applied for B4.

[Diagram]
White's tesuji  

W5 threatens capture of more than enough eye space, so Black must capture.

[Diagram]
White first to live  

W7 threatens to capture again so Black fills in, but it's a connect-and-die - W9 finishes the job since Black can't escape.

dent: I don't understand why Black is compelled to play at B8 here and die. Why not as Black just connect at W9? Then recapture the White capturing stone at B8 and connect after?

Dieter : yes that would be better but then white lives by capture three to make An eye. This variation shows what happens if B tries to prevent that.


[Diagram]
Dent's Question 1  
[Diagram]
Dent's Question 2  

This seems like a much better outcome for Black than the final diagram in the solution. Connecting at a might not even be the best move on the board for Black. What am I missing?

[Diagram]
Better endgame for black if he can read  

Uberdude dent: you are missing that if black is able to read that he can't kill, it would be better to not lose points trying but simply play as shown left, as this is better for black than the result in "Dent's Question 2" (more black points in corner, fewer points for white). However, as a more advanced point, black shouldn't play this too early as a move at a is sente to kill with the attachment posed in the problem, and there is a chance that move could be useful on the outside later.


[Diagram]
Reference diagram  

splice: Small technicality. Karl's comment: "W5 threatens capture of more than enough eye space ...". As far as I can read, anything less will leave White with one eye. To wit:

[Diagram]
Not enough  
[Diagram]
Not enough pt 2  

So playing until the black stone is hit is not more than enough eye space, it's actually just enough. At least, the way I see it :)


[Diagram]
Not enough (Correction)  

unkx80: In the diagram entitled "Not enough", W3 is wrong, but B4 is also wrong. W5 lives.

aigo: Following the same line of logic, W7 is another mistake, it should go where B8 is to make an eye instead of capturing the black stone.

unkx80: Yes.

[Diagram]
Not enough (Correction)  

B4 should be played here. Subsequently, if White a, Black throws in at B2 and the eye becomes a false.


[Diagram]
Just enough  
[Diagram]
Just enough pt 2  

This way White has just enough space to make a second eye.

[Diagram]
I think this works...  

I'm just a beginner, but I've played through a bunch of variations here. If black attempts to atari W5 white can play double atari at a. If black attempts to connect in any way at a, b, or c, white can capture at least the three black stones on the first line to make another eye. Am I missing anything?

-- Brent Amersbach

[Diagram]
Better shape for black  

Shaydwyrm: This basically works the same way as the throw-in Karl showed above, but allows black an extra move on the outside. This may not matter, if black is strong on the outside, but it may matter an awful lot if white can mount an attack later on black's outside group. In other words, exchanging W5 for B6 gives black better shape on the outside than just exchanging W7 for B5, while gaining no real benefit for white. Just as a question of life and death, however, W5 does seem to work fine.

[Diagram]
Even better shape for black  

I think this variation gives way too much to black to be considered. He follows W9 with a and controls the corner, which was not the case with the original solution. Once white finally threatens the corner with b, black safely fills in W9. If white plays b earlier by playing W7 at b, black plays B8 at W7. Then if white plays next at B8 or W9, black still responds with a and controls the corner, and actually makes white's group dead. If white plays W7 at W7, then W9 at b instead, black follows by playing at W9 (or a), white plays at W7, and black secures the corner with a (or W9) again. The b position really does need to be played at move W5.

-- Syndrina

[Diagram]
I think this (doesn't) work...  

Moosky: for the "I think this works..." diagram, here is why it doesn't. Black connects at B6 and now just count the liberties for the black group (circles) and W5 (squares). Black would capture W5 before White can eat the Black group, and so the entire White group dies.

[Diagram]
This doesn't doesn't work...  

Uberdude: Actually Moosky, black dies with all the corner stones with your black 6 if white then extends to 7. So 5 can live, but it's better to directly throw-in at 6 as Shaydwyrm correctly explained above.



Beginner Exercise 19 / Solution last edited by 80.6.183.4 on May 27, 2016 - 16:22
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