GAP Forum: Matrice powers

> < ^ Date: Wed, 16 Jul 2003 15:34:54 +0200
> < ^ From: Nicola Sottocornola <Nicola.Sottocornola@wanadoo.fr >
> ^ Subject: Matrice powers

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Dear GAP-Forum,

I have a programme starting with

Indeterminate(Rationals,"x");;
p:=UnivariatePolynomial(Rationals,[1,-2,-2,-2,1],1);;
e:=FieldExtension(Rationals,p);;
t:=RootOfDefiningPolynomial(e);
si:=2*t/(1+t^2); co:=(1-t^2)/(1+t^2);
idm:=IdentityMat(5,e);; 
A:=idm*[[0,0,0,0,1],
[1,0,0,0,0],
[0,1,0,0,0],
[0,0,1,0,0],
[0,0,0,1,0]];;

I don't understand why I obtain the following output

gap> A^(-1);
Error, no method found! For debugging hints type ?Recovery from
NoMethodFound
Error, no 2nd choice method found for `INV_MUT' on 1 arguments called from
<function>( <arguments> ) called from read-eval-loop
Entering break read-eval-print loop ...
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
brk>

while I can compute positive powers of A.

Thanks, Nicola

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Dear GAP-Forum, 
 
I have a programme starting with 
 
Indeterminate(Rationals,"x");; 
p:=UnivariatePolynomial(Rationals,[1,-2,-2,-2,1],1);; 
e:=FieldExtension(Rationals,p);; 
t:=RootOfDefiningPolynomial(e); 
si:=2*t/(1+t^2); co:=(1-t^2)/(1+t^2); 
idm:=IdentityMat(5,e);;  
A:=idm*[[0,0,0,0,1], 
[1,0,0,0,0], 
[0,1,0,0,0], 
[0,0,1,0,0], 
[0,0,0,1,0]];; 
 
I don't understand why I obtain the following output 
 
gap> A^(-1); 
Error, no method found! For debugging hints type ?Recovery from
NoMethodFound 
Error, no 2nd choice method found for `INV_MUT' on 1 arguments called
from 
<function>( <arguments> ) called from read-eval-loop 
Entering break read-eval-print loop ... 
you can 'quit;' to quit to outer loop, or 
you can 'return;' to continue 
brk> 
 
while I can compute positive powers of A. 
 
Thanks, Nicola 
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