On Nov. 23, Juan Pablo Carbajal wrote:
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Is there anyway to simplify
diff('sum(A(i)*k(t,i),i,1,3),k(t,j));
to A(j) ?
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This may not be what you are looking for,
but, for what it is worth:
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(%i1) sdiff (asum, var, nv ) :=
block ([summand, dummy, term ],
summand : part (args (asum), 1),
dummy : part (args (asum), 2),
term : part (args (var), nv),
expand (subst (dummy = term, summand)/var))$
(%i2) ee : 'sum (A(i)*k(t,i), i, 1, 3);
(%o2) 'sum (A(i)*k(t,i), i, 1, 3)
(%i3) sdiff (ee, k(t,j), 2 );
(%o3) A(j)
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Best Wishes,
Ted Woollett