4-1.Complex numbers
easy

सम्मिश्र संख्या $z = \sin \alpha  + i(1 - \cos \alpha )$का कोणांक हैं

A

$2\sin \frac{\alpha }{2}$

B

$\frac{\alpha }{2}$

C

$\alpha $

D

इनमें से कोई नहीं

Solution

(b) $z = \sin \alpha  + i(1 – \cos \alpha )$

$⇒amp(z) = {\tan ^{ – 1}}\left( {\frac{{1 – \cos \alpha }}{{\sin \alpha }}} \right) = {\tan ^{ – 1}}\left( {\frac{{2{{\sin }^2}\frac{\alpha }{2}}}{{2\sin \frac{\alpha }{2}\cos \frac{\alpha }{2}}}} \right)$

$ = {\tan ^{ – 1}}\tan \left( {\frac{\alpha }{2}} \right) = \frac{\alpha }{2}$.

Standard 11
Mathematics

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