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4-1.Complex numbers
easy
If ${i^2} = - 1$, then sum $i + {i^2} + {i^3} + ...$to $1000$ terms is equal to
A
$1$
B
$-1$
C
$i$
D
$0$
Solution
(d) $i + {i^2} + {i^3} + …….$up to $1000$ terms
$ = \frac{{i(1 – {i^{1000}})}}{{1 – i}} = $$\frac{{i(1 – {{({i^4})}^{250}})}}{{1 – i}}$$ = \frac{{i(1 – 1)}}{{1 – i}} = 0$.
Standard 11
Mathematics