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4-1.Complex numbers
easy
The argument of the complex number $\frac{{13 - 5i}}{{4 - 9i}}$is
A
$\frac{\pi }{3}$
B
$\frac{\pi }{4}$
C
$\frac{\pi }{5}$
D
$\frac{\pi }{6}$
Solution
(b)$arg\left( {\frac{{13 – 5i}}{{4 – 9i}}} \right) = arg(13 – 5i) – arg(4 – 9i)$
$ = – {\tan ^{ – 1}}\left( {\frac{5}{{13}}} \right) + {\tan ^{ – 1}}\frac{9}{4} = \frac{\pi }{4}$
Standard 11
Mathematics