Gokyo Shumyo, Section 1, Problem 87 / Solution

Main line  

After , White can't play at a because of the snapback.

Continuation  

So Black captures and can connect at if White ataris at .

Variation 1  

If White connects at , and captures the three stones including (White a, Black b).

Variation 2  

White can not play this way because the marked black stone assures the second eye at the circled point.

Failure at 7  

The order of play is important here. If Black tries to get a stone at first, then gives atari, White's shortage of liberties has vanished. She plays to make miai of cutting at a or saving the cutting stones at b.

Failure at 7 (ii)  

Here, White simply connects and has one liberty more than the 4 stones in atari.