RTG Problem 77 / Attempts

Tesuji  

Herman: Black has an obvious gote eye at a, and since there is no way to connect, black will have to find a way to make an eye in sente, the most obvious area being the lower left corner. I think the tesuji of will do the trick

Separation  

If White attempts to prevent black from making an eye with , then will cut off white's stones.

Connecting out  

Although white can live with through , black can then cut at a, connecting his group and saving it that way.

unkx80: Isn't it better to play at , killing all the white stones?

Herman: You're absolutely right! I thought it led to ko, but it doesn't :)

Life  

If white connects with as in this diagram, then with and , black makes an eye, and and become miai for the second eye.

This is better for white than the previous diagrams.

unkx80: I expect that the best white move to be at , black plays the same , then can be played at a.

Herman: Yes, that is better indeed

In-between move  

Bill: How's this?

unkx80: True also, I missed this.

A second question: in typical cases, isn't better directly played at a?

Bill: Yes, you're right. :)

Better, as a rule  

captures , then White can force up to . Later, will normally be sente. Black gets 3 points locally and White gets 1 point at .

Not so good  

After White can force up to . Later is sente. The net local score is the same, since Black gets 2 points while White does not get 1 point at . However, Black no longer has the sente in the center. As against that, may not become territory.

BTW, the quick way to see that in the first diagram is at least as good in the second one is the fact that in the second one White can play at 3, forcing at 2 and transposing to the first diagram. :)