Since 1 was the vital point in Gokyo Shumyo, Section 1, Problem 10 / Solution, and Black neglected playing there, White may think first of playing there. And a good idea it is. Black's only resistance is 2, but White 3 makes miai of A and B, where the continuation Black A White B results in a bent four in the corner.
White 1 here is wrong. Black remembers the vital point and plays 2. 3 and 4 are kind of miai. After 4, White can't connect at A, for capturing four stones will give Black a second eye.
Now even if throws in at , Black has two eyes.
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