The value of (−i)13 is
Since −√3−i2=-(cosπ6+isinπ6)
⇒ (−√3−i2)3=-(cosπ6+isinπ6)3=-i
And √3−i2=(cosπ6+isinπ6)
And (−√3−i2)3 =(cosπ2+isinπ2)=-i
Hence the result