Question: How can i sum an expression numerically

Dears. I want to evaluate the following expression numerically
G[i]=sum(Gama[i,k], k=1..100, k<>i),
where
Gama=((x[k]-x[i])*xdot[k]+(y[k]-y[i])*ydot[k])*dtheta[i]/((x[k]-x[i])^2+(y[k]-y[i])^2)^2
Dr. Amr
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