4-1.Complex numbers
medium

જો $z,w$ એ સંકર સંખ્યા છે કે જેથી $\overline z + i\overline w = 0$ અને $arg\,\,zw = \pi $ તો arg z મેળવો.

A

$5\pi /4$

B

$\pi /2$

C

$3\pi /4$

D

$\pi /4$

(AIEEE-2004)

Solution

(c)Given that arg zw =$\pi $ …..$(i)$
$\bar z + i\bar \omega = 0 \Rightarrow \bar z = – i\bar \omega $$ \Rightarrow z = i\omega $$ \Rightarrow \omega = – iz$
From $(i)$, arg$( – i{z^2}) = \pi $
$arg\;( – i) + 2arg(z) = \pi $ ; 

$\frac{{ – \pi }}{2} + 2\;arg(z) = \pi $
$2\,arg\,(z) = \frac{{3\pi }}{2}$; 

$a\,rg(z) = \frac{{3\pi }}{4}$

Standard 11
Mathematics

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