KyuExercise49/Attempts

The beginning?  

tderz: As you prove below (or Ed?), these variations above are not equal.

According to Go heuristics (proverbs), most players would first try to make the possible eye space smaller,
hence here (if you go for the bent-4 theme).
If then any other reply than the here, it is easy to see that 3-in-a-row, even if in the corner, will die.
Then comes your key point (vital point) as demonstrated by Ed? in diagram [1#1] below.
All other diagrams give too much leeway to Black, e.g. not-dead(ko)-wise or be it liberty-wise (bulky 5).

Speaking of liberties, bent-4 gives Black the most liberties (≈ ∞ ?), because even under Japanese Rules, White had to wait until the end, before claiming the group without ko. If a fight involving the outer white group occurred (a cutting point at c is present), then this is clearly inferior to a solution with normal death (involving finite liberties n).
Hence, one would think Ed?'s diagram ^[2]ff is the correct solution,
just to realize that (only) sequence ^[3] assures death and avoids ko ^[4].

Still, in ^[2] is also an eye-space reducing move in first instance.

This was my incentive to put across here:

• think first of reducing eye space (hane, block ...),
• then think of vital points.

I think this usually holds and at a certain moment you think at both anyway.

Push - white mistake => ko  

tderz White misses the -- combi of Ed?'s diagram ^[3](not easy and in that order only) and only gets ko.

Conclusion: This is an exercise for Maeda-kyu players only. (any problem involving bent-4)

Ko?  

P7A77: Looking at it now, I think leads to Ko.

Even Goofier  

P7A77: And this is even messier. Okay, so, any other thoughts...?

Ed?: In this diagram black is alive in double ko. should be at to kill with a bent 4.

Seki or ko  

Ed?: Black dies if is played at 'a', white 'c' forces seki, white 'b' gives white the choice of seki or ko.

Reduce eye-space  

[2] Ed?: reduces black's eye-space

Black maximises eye-space  

Ed? 'a' and 'b' are miai to kill. If at black lives by playing at himself.

Alternative for  

White can create a dead shape

Another alternative for  

Ed?: at would lead to ko.

Black takes vital point  

[3] tderz is a simple key point, but easy to be missed.

Push  

Ed?: here also leads to a bent 4 shape. [1]

Push - white mistake  

[4] here gives black a ko.