Evaluate

Question:

Evaluate $\left(1+i^{10}+i^{20}+i^{30}\right)$

 

Solution:

We have, $1+\mathrm{i}^{10}+\mathrm{i}^{20}+\mathrm{i}^{30}$

$=1+\left(i^{4}\right)^{2} \cdot i^{2}+\left(i^{4}\right)^{5}+\left(i^{4}\right)^{7} \cdot i^{2}$

We know that, $i^{4}=1$

$\Rightarrow 1+(1)^{2} \cdot i^{2}+(1)^{5}+(1)^{7} \cdot i^{2}$

$=1+i^{2}+1+i^{2}$

$=1-1+1-1$

$=0$

 

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