Beginner Exercise 136 / Solution

White to play.  

mgoetze: With a throw-in, white can set up a double ko in which she will definitely capture something. Whenever Black plays a, White can play ; if Black ever plays b, White will be able to capture at c or d.

Rich: If Black captures with b, d would be an illegal move...

mgoetze: Oh... mumbles something about sleep deprivation... well, uhm, at least it will be a good source of ko threats.

unkx80: The moves can be considered correct. To nitpick a bit, can be played more profitably at a.

There is an alternative solution below, which may be better:

Solution.  

White plays , then a and b are miai. One good thing about this is that White does not have to sacrifice any stones prior to .

Losing the ko.  

In mgoetze's diagram, if is played at , then White's loss when losing the ko is to the extent of . This will not happen in the solution diagram.

zxb: To me, you should play throw-in on the side that is smaller, less important. That is, the side that ko fight will inevitably occur. The difference is who takes the ko first. For example, let's assume here, that the right side is more important. If you don't play throw-in, then black will capture the right side, and you have a ko fight on the left side. However, in this case, black takes the ko first. If you do play throw-in on the left side, the outcome is the same, except that white takes the ko first.