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February 1999's Go Answer of the Month

Dia 1 - Seven space big eyes.

A more convoluted question this month. I hope you know the answer to the first part without having to think about it.

• What is the status of the 7 space big eyed group on the right?
• Is A or B bigger? What are they worth?
• What aji exists on the right half of the problem for Black? for White?
• Does the answer to the above alter as the outside liberties of the White big-eyed group are removed by Black?

Dias 2 & 3 - Status.

White can live in gote. Black can get a gote seki (White 2 elsewhere). After either, White gets probable sente pushes at A, B and C.

It is theoretically possible for Black to almost fill this big eye with a rabbitty six, thus killing White. But it is unlikely that would happen. If White should tenuki with 4 in Dia 3, then Black cannot be prevented from doing this so that White is now dead. It actually takes Black 20 moves to remove the White stones if a capturing race occurs and White would be beter off with the seki in that case.

Dia 4 - A or B?

Playing at A is worth 6 points in gote as shown in Dias 2 & 3.
Playing at B captures 4 stones, again in gote. Later on another gote move for White connects the capturing stones or a Black gote move recaptures one stone. The net result is somewhere between 5 and 7 points for White.

If these were the only plays left on the board the plays are:

• Black A, White B, Black captures at C, White D, Black connects at B. White gets 5 points.
• Black B, White A. White gets 6 points.
• White A, Black B. White gets 6 points
• White B, Black A, White connects at C. White gets 7 points.
• White B, Black captures at C, White A, Black D, White E, Black connects at B. White gets 10 points.

The last sequence is bad for Black. The others suggest that playing at B is one point better than playing at A.

Dias 3 again & 5 - Aji?

Once Black has played 1 in Dia 3, the first player to play again has two ko threats. Black gets two large ko threats - 3 and 5 threatening to kill White. White gets two small ko threats in Dia 4 - 2 and 4 threatening to live with 6 points.

And the status doesn't alter as the outside liberties are removed.

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