Gokyo Shumyo, Section 1, Problem 70 / Discussion

Is White 1 wrong ?  

From Gokyo Shumyo, Section 1, Problem 70. I can't find the refutation for , but it is late too. --Dieter

Attempt 1: the hane  

Let us consider this to be the basic variation (involving no ko). We will reconsider and . and are miai. is clearly wrong: takes the vital point. If now Black a, White has enough outside liberties to capture Black's bent four. If Black doesn't play a, White a makes seki.

Variation at 7  

here is better: White cannot connect because after either Black a will almost fill with a bulky five or White a dies in gote.

Variation at 7 - White's best try  

This results in ko. in "Attempt 1" is forced (for otherwise Black makes a bent three inside eye). So we look for a variation at w4.

Variation at 4  

This is the first alternative. It looks like White can escape, but up to her position is hopeless.

Variation at 4  

But here is better: a and b are miai: Black a - White b is symmetrical to the first diagram and Black b - White a gives White the time to capture the three stones and make two eyes.

Variation at 4 - Black's best  

assures ko. At the moment I am not able to tell if it will become double ko (which means life) or not. This surely means I don't understand ko.

(Sigh) Let's suppose it is some sort of ko, still worse than unconditional life. Then we must proceed to an alternative for in "Attempt 1".

Variation at 2  

Since was the correct move in Gokyo Shumyo, Section 1, Problem 70 / Solution, chances are that it saves the day again. Given Gokyo Shumyo, Section 1, Problem 70 / Solution, is not the answer, but obviously White at will make two eyes.

Attempt 2: the vital point  

Please do some of the work. I may continue later.