After , Black tries to capture her stone with . White answers calmly at .
What should Black do next?
If Black plays at , White cuts through his position with . Black has to answer at and , otherwise he loses the six black stones on the left.
So, applying the proverb "Your opponent's good move is your good move" Black might try to protect against White by playing at .
After Black's group is in shortage of liberties and Black cannot connect (White would capture at a).
So, Black cannot capture the original white stone, but instead has to save his own stones.
Note that White still has some good aji around this area.
Lo! Behold AvatarDJFlux!! Praise to the Finder Of The Much Difficult Black Answer At 175!!%%% ;-)))