4-1.Complex numbers
normal

સંકર સંખ્યા $\sin \,\frac{{6\pi }}{5}\, + \,i\,\left( {1\, + \,\cos \,\frac{{6\pi }}{5}} \right)$ નો કોણાક મેળવો 

A

$\frac{{6\pi }}{5}$

B

$\frac{{5\pi }}{6}$

C

$\frac{{9\pi }}{10}$

D

$\frac{{2\pi }}{5}$

Solution

$\sin \frac{6 \pi}{5}+i\left(1+\cos \frac{6 \pi}{5}\right)$

lies in ${2^{nd}}$ quadrant and

$\left|\frac{1+\cos \frac{6 \pi}{5}}{\sin \frac{6 \pi}{5}}\right|=\left|\cot \left(\frac{3 \pi}{5}\right)\right|=\left|\cot \left(\frac{\pi}{2}+\frac{\pi}{10}\right)\right|=\tan \frac{\pi}{10}$

${2^{nd}}$ quadrant $\Rightarrow \pi-\frac{\pi}{10}$

Standard 11
Mathematics

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