Help with old Mathematica file

[Zsolt Ero]

I am trying to solve a problem, for what I finally found a book what has some Mathematica files supplied, but I am stuck now as I cannot run the file.

My problem is that I cannot run the program as it is written in Mathematica 3.0 and I don't know what should I change to make it run under today's Mathematica versions. Here is the error it returns.

> FindMinimum::fmgz: Encountered a
> gradient that is effectively zero. The
> result returned may not be a minimum;
> it may be a maximum or a saddle point.

The file is called Programs\MOTIPOIN.NB in this file: http://bit.ly/lMQh1K

or alternatively, here is a pastebin for the code in question: http://pastebin.com/ASBXnVVS

Can you have a look at what could be wrong with the code? Its only 50 lines, but I don't know how to fix it.

[Patrick Scheibe]

Hi,

in line 26 and 27 you try to find a minimum of a function z and you are
starting at t=0 which is a maximum. There, the derivative is zero and
FindMinimum doesn't know where to walk.

Try setting

FindMinimum[z, {t, 0.01, 0, b trif}]

and don't try to adapt the programming style of this book, please.

Cheers
Patrick

[Zsolt Ero]

Hi Patrick,

Thanks, it seems to work! Is there any way to display the graphs it generates inside the module? I think originally it was made to show you the resulting graphs, but now with ; after the plot functions it doesn't display anything.

Zsolt