Gokyo Shumyo, Section 1, Problem 58 / Solution

Main line  

White enlarges her eye space with , then makes eye shape with . Incidentally, and makes a notcher with code 411WN.

If White descends at a instead of move , then White is also alive. However this way is less good for White, as Black can profit by capturing two stones. See problem 28 in this series for details.

Continuation - variation 2  

at a also works.

Failure at 3  

The solid connection at fails. Black a to d all kill. (This shape is coded 312NS notcher.)

Failure at 3 (punished)  

For example, strikes at the vital point. After , a and b are miai.

Failure at 3 (punished)  

If White enlarges her eyespace, there are many ways to kill. For example, and leads to some nakade shape.

Failure at 3 (wrong punishment)  

hane from the left fail to kill. secures seki.