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Beginner Exercise 4 Solution
  Difficulty: Beginner   Keywords: Problem

KarlKnechtel, filling in a solution.

[Diagram]
Solution.

Quickest explanation (not at all useful to those for whom this was challenging): "W1 is tesuji. B2 and W3 are miai for the kill."



How I'd explain it to someone a bit below my level: "The throw-in at W1 threatens to capture BC. Black cannot connect because he is in shortage of liberties - B2 at W3 is answered by the capture with W3 at B2. So Black captures, making one eye; but W3 destroys the other eye."

In easier terms: Black needs two eyes to live. There is already effectively one at a. White must prevent the centre space from becoming an eye. The sacrifice changes the shape of that space, achieving the goal.

This problem is small enough that we can consider all the alternatives:

[Diagram]
Reference.

Playing elsewhere is answered by Black either at a or b. (b claims an extra point of territory, at the expense of one ko threat (at a) for White[1]. So clearly White has to do something.

(Incidentally, the eye around a is an example of what I call a two-space elbow. Not that it really matters.)


[Diagram]
Failure.

One try is to threaten the existing eye; but the capture solves all of Black's problems. (On the other hand, connecting at a would be very bad for Black; White doesn't even have to capture.) This is also a throw-in, but it's the wrong one and doesn't help.


[Diagram]
Failure.

Moving to make the other eye false looks good at first, because Black is in atari to start off with. But all Black has to do is connect. Again, the two eyes are solid.


[Diagram]
Good for white?

I'm new to go but enjoying learning about it a lot. The above confuses me a little. Could someone explain why the sequence W1, B2, W3 isn't good for White? Is it that Black would really have played B2 at W3 resulting in a ko? --DaveFinlay

Answer: W3 is a forbidden (suicide) move now. It is placing a stone at a point without any liberties while not capturing any stones.

Thanks. I don't know what I was thinking. DaveFinlay



I'm really new to Go (just started learn last week). I'm a little confused about the terminology "played B2 at W3". What does that mean? I guess that B2 is same as the numbered black stone, but what does "at W3" mean?

Confused: It's a convenient shorthand for describing simple variations of a diagram. B2 at W3 means, the situation if Black would have played the second move (B2) at the location of the White stone at W3. Here Karl Knechtel was writing about the following case.

[Diagram]
Situation after B2 at W3.


Jasonred (I think) wrote:

tesuji or nakade?

Confused: It's a tesuji, although I'm not sure if that play counts as nakade too. If the definition on the nakade page is correct, I'd say it isn't one.

This is one of the reasons, why I avoid throwing around Japanese terms I don't understand completly or for which there is a good English translation. Some of those concepts are complicated enough on their own, that I don't need to confuse the matter more with the wrong Japanese names.

It's a throw-in


[1] A black play at a is safe from that, as I'd originally thought, but I managed to confuse myself somehow. Thanks SAS. :) Anyway - see Points Or Ko Threats Discussion for more information about that sort of tradeoff.

unkx80: I think that b is better than a in the context of this question, for two reasons: (1) It claims an extra point of territory, (2) It creates a cutting point. The group in Points Or Ko Threats Discussion is different in the sense that either of the two points there has equal value except for ko threats, so the one giving less ko threats might be better.
Coyote?: Depending on the situation, I would go with "b". That is - if I have more Ko threats then my opponent, especially if the threat of the cut can give me Sente. If it looks like my opponent is getting more Ko threats then me, I can still close it off, losing the point of territory. But not until I have to, because whether now or later, the move is Gote. - Coyote, 17kyu



This is a copy of the living page "Beginner Exercise 4 Solution" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.