Dear Gap-forum, and Nicola,

I would express the algebraic numbers occuring in your example in a
suitable cyclotomic field (see E and CF in the manual); in your case 
CF(20) should do; for instance, cos(t) and sin(t) should be sg like
this:
c1:=(-E(5)^2-E(5)^3)/2;
s1:=(-E(5)^2+E(5)^3)/(2*E(4));
Then define A and S, and simply call Size(Group([A,S])).

Best wishes,

Jan

Dear GAP forum,

I'd like to generate a group using two elements A and S: G = <A,S>. I
don't know if this group is finite. Someone can help me?

S = diag(1,1,-1,-1)

A =
[0,                 0,             cos(s),     -sin(s)]
[-sin(t),         cos(t),             0,             0]
[cos(t),         sin(t),             0,             0]
[0,                 0,             sin(s),     cos(s)]

with

cos(t) := 1/4 + 1/4 sqrt(5)

sin(t) := 1/4 sqrt(2) sqrt(5 - sqrt(5))

cos(s):= 3/4 - 1/4 sqrt(5)

sin(s):= 1/4 sqrt(2 + 6 sqrt(5))

Thank you, Nicola.

Miles-Receive-Header: reply