Life In 19x19

So here's the problem on pg 59, black to play:

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[go]$$B Position 17
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$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O . . . O O X . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ ---------------------------------------[/go]

After a few failure diagrams, it shows this success:

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[go]$$B Diagram 5
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$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O . 4 6 O O X . . . . . . . . . |
$$ | . 7 5 . 2 1 3 . O . . . . . . . . . . |
$$ ---------------------------------------[/go]

But then it has this diagram:

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

"From the result of Diagram 1 it can be appreciated that black 1 is a vital point. After the sequence white 2 to black 5, A and B are equivalent options and white is dead."

It doesn't seem like this move works to me:

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

The other move (diagram 5) seems like the right answer. Is this a mistake in the book or am I missing something? Does starting at either point work?

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[go]$$B Killed
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$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O 6 3 5 O O X . . . . . . . . . |
$$ | . . 7 . 4 2 1 . O . . . . . . . . . . |
$$ ---------------------------------------[/go]

Black just connects, as above, the rest is inevitable.

You're right, I should have noticed that. So I guess both moves work?

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[go]$$B Killed
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$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O 4 3 6 O O X . . . . . . . . . |
$$ | . . 8 . 5 7 1 . O . . . . . . . . . . |
$$ ---------------------------------------[/go]

I'm not sure, what about this seki? (2 at 7) Suggests the best b can do here is 7 at 8 and then fight the ko.

Stable wrote:

$$B Killed
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$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O 4 3 6 O O X . . . . . . . . . |
$$ | . . 8 . 5 7 1 . O . . . . . . . . . . |
$$ ---------------------------------------

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[go]$$B Killed
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O 4 3 6 O O X . . . . . . . . . |
$$ | . . 8 . 5 7 1 . O . . . . . . . . . . |
$$ ---------------------------------------[/go]

I'm not sure, what about this seki? (2 at 7) Suggests the best b can do here is 7 at 8 and then fight the ko.

Your 5 looks wrong to me.
Oh I missed there was a 2 at your 7.

Never mind.

I misinterpreted some English.

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[go]$$B Death in the hane
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O 7 4 3 O O X . . . . . . . . . |
$$ | . . 5 6 . 2 1 . O . . . . . . . . . . |
$$ ---------------------------------------[/go]

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[go]$$B Variation
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$$ | . X . , X X X . . , . . . . . , . . . |
$$ | . . X X O O O X X X . . . . . . . . . |
$$ | . X O O . 4 3 O O X . . . . . . . . . |
$$ | . 7 5 . 6 2 1 . O . . . . . . . . . . |
$$ ---------------------------------------[/go]

Thanks Bill!