Life In 19x19

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[go]$$B Black to play first. Choose between a and b
$$ --------------------
$$ |. . . . . . . . . .
$$ |. a O O b . . . . .
$$ |. X X O X . . . . .
$$ |. O O X X O . . . ,
$$ |. . . . . . . . . .
$$ |. . X . . . . . . .
$$ |. . . . . . . . . .[/go]

I'm currently studying Lee Chang Ho Course, middle level, book 1 and stumbled accross the above problem in lesson 7.

The correct answer is A. Anyone any idea why A is eventually better than B ?

Either way white must capture the corner stones and black gets to play B. But if A is on the board then white cannot later hane and connect at the top so that becomes black's privilege later.

Thanks DrStraw for seeing the better yose continuation, that's the kind of thing I need to improve.

Also there is one extra (rather big) ko threat left there if black plays the correct move.

Probably a question indicative of bad hibits, but are there cases where black might want to play b because if black plays a white will play b first?

Click Here To Show Diagram Code

[go]$$B Black to play first. Choose between a and b
$$ --------------------
$$ |. . . . . . . . . .
$$ |. 1 O O 2 . . . . .
$$ |. X X O X . . . . .
$$ |. O O X X O . . . ,
$$ |. . . . . . . . . .
$$ |. . X . . . . . . .
$$ |. . . . . . . . . .[/go]

illluck wrote:Probably a question indicative of bad hibits, but are there cases where black might want to play b because if black plays a white will play b first?

Click Here To Show Diagram Code

[go]$$B Black to play first. Choose between a and b
$$ --------------------
$$ |. . . . . . . . . .
$$ |. 1 O O 2 . . . . .
$$ |. X X O X 4 . . . .
$$ |. O O X X O . . . ,
$$ |. . 3 . . . . . . .
$$ |. . X . a . . . . .
$$ |. . . . . . . . . .[/go]

If W has positions on both sides this is conceivable, but I think the point of the exercise was the best way to force W to capture the corner. Also, given the B has a nice shape move at A it is hard for W to play this way.

Click Here To Show Diagram Code

[go]$$B
$$ --------------------
$$ |. 4 . . . . . . . .
$$ |6 1 O O 2 . . . . .
$$ |. X X O X 3 . . . .
$$ |. O O X X O . . . ,
$$ |. . 5 . . . . . . .
$$ |. . X . . . . . . .
$$ |. . . . . . . . . .[/go]

Black might also answer because you helped him damage your outside stone, and 5 in sente is huge. In the usual joseki by blocking at the top in sente the left block is no longer sente so there is a cut on the left. I once lost a game and a tournament and about £50 because I misjudged the severity of this cut.

Click Here To Show Diagram Code

[go]$$B
$$ --------------------
$$ |. 2 . . . . . . . .
$$ |4 1 O O 3 . . . . .
$$ |. X X O X . . . . .
$$ |. O O X X O . . . ,
$$ |. . . 0 . . . . . .
$$ |. . X . . . . . . .
$$ |. . . . . . . . . .[/go]