Gokyo Shumyo, Section 1, Problem 6b / Solution

White to kill  

I suggest . It removes all aji that existed in some variations, Black playing and threatening a cut at a.

White to kill  

And it kills, of course. Black's only resort was to play at , but after the forced sequence up to , he can't give atari at a, nor at b, because of shortage of liberties.

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