gaussian quadrature

[Antonio]

Hello Didier,

Thanks for the reply.

Regarding the program 1 , what I mean is that sometimes it runs and calculates the roots and coefficients and sometimes fails to execute
M2:=CAS.zeros(legendre(nr)); or
F1:=CAS.diff(legendre(nr));
does not give any error message unless it does not.

Regarding the program 2, I tried to change x by X , as you suggested, I had to add one more line to assign the value to the X ,as it does not properly
a0:=subst(diff(legendre(nr)),X=M2(i));

they work as

X:=M2(i);
a0:=subst(diff(legendre(nr)),X=0);

Another problem is that not running the loop, and I 've been manually deactivated by assigning values ​​to the variable i, work when i = 2 or i = 3 , but not when i = 1, the error is in

M1(i,1):=2/((1-M2(i)^2)*(a0^2));
and I dont see the failure more I look.