According to the formula:
i^(4n)= 1
i^(4n+ 1)=i
i^(4n+2)=- 1
i^(4n+3)=-i
You can know:
i^ 165=i^(4*4 1+ 1)=i
i^200=i^(4*50)= 1
i^278=i^(4*69+2)=- 1
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