Fran's Life and Death Problem #136.. Can you solve it?

[Jordus]

The problem is labeled as a 10k level. Apparently I couldn't think well enough today to solve it. Can you?

$$Wc White to form life
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$$ | . O X . X . . . .
$$ | . . O O X . . . .
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$$ - - - - - - - - - -

Click Here To Show Diagram Code

[go]$$Wc White to form life
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$$ | . X X . . . . . .
$$ | . O X . . . . . .
$$ | . O X . X . . . .
$$ | . . O O X . . . .
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$$ - - - - - - - - - -[/go]

Answer:

You should have seen my face when I solved it... Doh!

$$Wc White to form life
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$$ | . X X . . . . . .
$$ | 3 O X . . . . . .
$$ | . O X . X . . . .
$$ | 1 . O O X . . . .
$$ | . 2 5 4 . . . . .
$$ - - - - - - - - - -

Click Here To Show Diagram Code

[go]$$Wc White to form life
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$$ | . . . . . . . . .
$$ | . X X . . . . . .
$$ | 3 O X . . . . . .
$$ | . O X . X . . . .
$$ | 1 . O O X . . . .
$$ | . 2 5 4 . . . . .
$$ - - - - - - - - - -[/go]

[Joaz Banbeck]

I forget which pro it was who said something like 'When in doubt about corner life...

...start your reading with the 1-2 and 2-1 points'. When I asked why that was, he said that it was an efficiency issue: those two points enclose the only eye that requires only three surrounding stones. All other eyes require more.

[Bki]

I forget which pro it was who said something like 'When in doubt about corner life...

...start your reading with the 1-2 and 2-1 points'. When I asked why that was, he said that it was an efficiency issue: those two points enclose the only eye that requires only three surrounding stones. All other eyes require more.

He is not in pro, but,

In his book (in French) Tsumego, Motoki Noguchi emphasize quite a bit how important the 1-2 points are in the corner. Not only because of it's the best point to make an eye, but also because it's also the best point to set a ko, and a descent to the 1-2 point will require an approach move by your opponent.

The 1-2 point is like, the second move I check after the hane and obvious vital points for an eye.

[jeromie]

I did get it. It's encouraging when I can solve tsumego I "should" be able to figure out.

In addition to the advice above:

When I notice a semi-symmetrical problem where one group has more liberties than the other, I generally try a move that reinforces the group that is short of liberties first. That gave me a good idea of which 1-2 point was likely to be correct before I started reading.

[PeterN]

Heh, the answer I got when asking some better players about the 1-2 points was generally along the lines of "Because they're magic." That's the first time I've actually seen a proper reasoning for it.

PeterN

[Cassandra]

The 2-1-points might become vital ...

$$ Bulky Five I
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$$ | M T O O X . . . .
$$ | T T . . . . . . .
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Click Here To Show Diagram Code

[go]$$ Bulky Five I
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$$ | M T O O X . . . .
$$ | T T . . . . . . .
$$ - - - - - - - - - -[/go]

$$ Bulky Five II
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$$ | . X X . . . . . .
$$ | . O X . . . . . .
$$ | . O X . X . . . .
$$ | T T O O X . . . .
$$ | T M T . . . . . .
$$ - - - - - - - - - -

Click Here To Show Diagram Code

[go]$$ Bulky Five II
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$$ | . X X . . . . . .
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$$ | T T O O X . . . .
$$ | T M T . . . . . .
$$ - - - - - - - - - -[/go]

As a matter of course, the liberty count matters ...

$$W
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$$ | . 3 X . . . . . .
$$ | . 3 X . X . . . .
$$ | . . O O X . . . .
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$$ - - - - - - - - - -

Click Here To Show Diagram Code

[go]$$W
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$$ | . . . . . . . . .
$$ | . X X . . . . . .
$$ | . 3 X . . . . . .
$$ | . 3 X . X . . . .
$$ | . . O O X . . . .
$$ | . . . . . . . . .
$$ - - - - - - - - - -[/go]

$$B
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$$ | . X X . . . . . .
$$ | . O X . . . . . .
$$ | . O X . X . . . .
$$ | . . 4 4 X . . . .
$$ | . . . . . . . . .
$$ - - - - - - - - - -

Click Here To Show Diagram Code

[go]$$B
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . X X . . . . . .
$$ | . O X . . . . . .
$$ | . O X . X . . . .
$$ | . . 4 4 X . . . .
$$ | . . . . . . . . .
$$ - - - - - - - - - -[/go]

[yang738]

there are two 2-1 points. find out the difference between these two points.