4-1.Complex numbers
normal

Let $z$ be a purely imaginary number such that ${\mathop{\rm Im}\nolimits} (z) < 0$. Then $arg\,(z)$ is equal to

A

$\pi $

B

$\frac{\pi }{2}$

C

$0$

D

$ - \frac{\pi }{2}$

Solution

(d)Let $z = 0 + ib$, where $b < 0$. Then $z$ is represented by a point on $OY'$ (negative direction of $y – $axis), therefore $arg(z) = – \frac{\pi }{2}$.

Standard 11
Mathematics

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