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4-1.Complex numbers
normal
$\sum\limits_{n - 1}^{50} {{i^{(2n - 1)!}}} $ is equal to (where $i = \sqrt {-1}$ )
A
$48$
B
$48 + i$
C
$47 + i$
D
$48+2i$
Solution
${i^{1!}} + {i^{3!}} + {i^{5!}} + {i^{7!}} + …. + {i^{99!}}$
$ = i + {i^6} + 1 + 1 + ……..1$
$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \leftarrow 48\,times$
$ = i – 1 + 48 = 47 + i$
Standard 11
Mathematics