Question
Evaluate the following : $i^{30}+i^{40}+i^{50}+i^{60}$

Answer

$i^{30}+i^{40}+i^{50}+i^{60}$
$
\begin{aligned}
& =\left(i^4\right)^7 i^2+\left(i^4\right)^{10}+\left(i^4\right)^{12} i^2+\left(i^4\right)^{15} \\
& =(1)^7(-1)+(1)^{10}+(1)^{12}(-1)+(1)^{15} \\
& =-1+1-1+1 \\
& =0
\end{aligned}
$

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