$\begin{aligned} & i+i^2+i^3+\ldots \ldots . \text { up to } 1000 \text { terms } \\ & =\frac{i\left(1-i^{1000}\right)}{1-i}=\frac{i\left(1-\left(i^4\right)^{250}\right)}{1-i}=\frac{i(1-1)}{1-i}=0\end{aligned}$