[CAS] sum

[compsystems]

with [CAS & EXACT MODE ON]

Σ(sin(n)/n,n,1,1000) =>
(1/7128865274665093053166 ...................
as it is difficult to visualize the answer, I convert to approximate
APPROX(ANS) => UNDEF

Now [CAS & EXACT MODE OFF]
Σ(sin(n)/n,n,1,1000) => 1.07069415432 ok