Gokyo Shumyo, Section 1, Problem 47 / Solution

Under the stones  

The solution includes an under the stones tesuji. After , a is a vital point.

Under the stones  

Black sacrifices two stones, hoping to destroy the eye by giving atari with at .

Under the stones  

White makes the surprising move at , allowing Black to capture four stones!

Under the stones  

In the space created by the four captured stones, White can recapture two stones.

Pitfall 1  

Obviously, White mustn't answer at here.

Pitfall 2  

If White hastily answers the atari by (temporarily) saving her stones with , kills.

No Under the stones  

If White fails to make the four-stone sacrifice, and connects at here, then takes three stones, and there is not enough room to play "underneath".

Failure  

makes one eye in the corner. makes miai of a and b to take away the other eye.

Inferior for Black  

here would allow White to live in ko.