Gokyo Shumyo, Section 1, Problem 43 / Solution

Main line  

The black group makes a comb formation with unfinished 'legs'. Here is the vital point.

Failure 1  

Knowing the comb formation tempts one to extend the leg with . White plays to create a bulky five and plays at the vital point.

Failure 2  

So, since the stone seemed to be the one spoiling the comb party, Black tries here. Up to he gets a ko.

Failure 3  

extending to enlarge his eyespace is careless. leads to ko.

Failure 4  

here may look to be a vital point....but and ! kills, with becoming double atari.