Thanks a lot for these informations.

There is a question which follows immediately:

If a, b, c element N and a² + b² = c² you can calculate tan (alpha)

and tan (alpha/2)

Is it possible to transform the tan (alpha/2) into a pyth. trippel with a*, b*, c*

I thought that a*, b*, c* should be element N again,

Example a=7, b=24, c=25 tan (alpha/2)=(c-b)/a=1/7

(very elegant solution!

)

But 1²+7²=50 so that c=sqrt (50) and c is not element N

On the other hand i thought that the pyth trippel form a group.

Somewhere there is a logical mistake.

Would be nice, if someone could give a hint.

Greetings from the pyth. trippel

Bernhard