# Diary, September 1999

```   Sun Mon Tue Wed Thu Fri Sat
1   2   3   4
5   6   7   8   9  10  11
12  13  14  15  16  17  18
19  20  21  22  23  24  25
26  27  28  29  30
```

## Thursday, September 9, 1999

### July 7, 1977

Today, I was phoned by a cousin of mine, who on this special day (9-9-99) had to think about another day like this more than 22 years ago, namely July 7, '77, when he was staying with us during the holiday. We recalled what we were doing those days. We tried to solve the
goat problem: how long should the cord be, to let a goat eat only the half of a circular field if the pole is on the boarder of the field. Or in other words: what is the radius of the circle which divide the unit circle on half, if the center of this circle is on the unit circle. We could not solve the problem at that time. This evening I though about it, and did find the solution, only using some elementary math. Only the following formulas are needed:
• Surface triangle equal to: ab.sin(gamma)
• Surface pie of circle: r.phi / 2
• Cosine rule: a2 + b2 - c2 = 2ab.cos(gamma)
• sin(gamma)2 + cos(gamma)2 = 1
With these you can derive the formula for the surface of a triangle given the length of the three sides:
sqrt(2a2b2 + 2a2c2 + 2b2c2 - a4 - b4 - c4) / 4
The goat problem is a special case of calculating the area of the intersection of two circle with radii r and s whoes center points are d apart. When two circle intersect there are four important points, namely the two center points of the circles, and the two intersection points. Lets look at the triangle made of one of the intersection points and the two center points. The sizes of all the sides are known, thus also the angles between them using the cosine rule. The area of the intersection equals the areas of the pies of the two circles minus the area of the triangles. This leads to the following formula:
s.acos((s2 + d2 - r2)/2sd) +
r.acos((r2 + d2 - s2)/2rd) -
sqrt(2r2s2 + 2r2d2 + 2s2d2 - r4 - s4 - d4) / 2
For the goat problem s = d = 1, and r is the requested radius. To find r, the following equation needs to be solved:
acos(1 - r2/2) + r.acos(r/2) - r.sqrt(4 - r2) / 2 = pi / 2
There are no analytical solutions to this equation.

## Wednesday, September 15, 1999

### Chestnuts

On my way to the cafeteria, which is on the otherside of the parking place, I could not help picking seven shining chestnuts that lay under some chestnuts trees on the border of the parking place. I put them in my pocket, and later when I returned to my working place, I laid them out on my computer. During the course of the afternoun they lost their shinging appearance, just like the once I found last year.

## Saturday, September 18, 1999

### Annabel and chestnuts

It looks like Annabel inherited my passion for chestnuts. We went to a chinese take-away restaurant, and while waiting for our order to be ready, Annabel went outside and started to collect as many chestnuts as she could. This was exactly the same place where we picked them last year.

## Friday, September 24, 1999

### Programming and art

What do have programming and art to do with each other?
Donald E. Knuth is writing a series of books with the title The Art of Programming. But is the act of programming an art, or just the application of well established rules to arrive at a working program.

Of course, the first requirement for programming is knowing the language. But that is the same with painting, knowing how to put paint with a brush on the canvas. For both one has to know the basic techniques, and in both fields there are people who stand far above all the others. In Advanced C++ programming styles and idioms James Coplien states "Style distinguishes excellence from accomplishment". This is true for both art and programming.

There is however one sad thing. Where the work of a painter can be valued by a lay person, the work of a programmer can only be valued by the experts. And yet another sad thing is that there is but only a weak correlation between the observable behaviour of a program, and the style of the code.

## Saturday, September 25, 1999

### Third Kabuki day

Today the third Kabuki day organized by the Dutch Kabuki Network. There were about 15 families present. We attended it for the second time. Last year we weren't sure about Andy's diagnoses yet. That made it a little different for now. What follows is a personal impression, and by no means complete. (For reasons of privacy, I will be vague with respect to refering to persons.)

The focus for this day was much on behavioural aspects. We had one short lecture explaining an investigation of behavioural aspects of childeren with KS. There are about 15 children joining in this academical study. This study will look into the cognitive abilities, the neuropsycological profile, and language abilities of the children. The "California Child Q-test" and the "Child Behaviour Checklist" will be used. Our son Andy (becoming two in a few weeks) is too young to join the test. Nevertheless, the people performing the research will have a look at him. The aim of the research is to come up with practical advise for the parents, but also a scientifical publication will follow.

After one hour of this, we had an extended lunch, after which we sat together to share about the development of and the problems with our children. This again showed how varied the Kabuki children are, but also some of striking similarities there are. Some children are slim because the eat slow. Others are on a diet because the eat too much. Eating seems to be an important topic for many Kabuki children. Two people reported problems with their child after being exposed to flashing lights. Of course, problems with the ears were discussed. One parent shared their experiences with a cosmetic operation on the ears of their child. Some other parents noted that temporarily stopping/reducing speech therapy can have a positive effect on the speech development.

It was good to come together and have ample time to talk and share. We will definitely go again next year. I realize that it is a blessing to live in a densely populated country. The average travel time for people to attend this day was only two hours.

(Second Dutch Kabuki day and Fourth Dutch Kabuki day)

## Tuesday, September 28, 1999

### Roses

The roses, which I gave to
Li-Xia on her birthday in May, are still producing a nice fragerence, I discovered to my surpries. The roses are almost dried completely. They have been standing in the living room all the time.

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