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Question: Answered & Verified by Expert
Amplitude of the complex number $i \sin \left(\frac{\pi}{19}\right)$ is
MathematicsComplex NumberCOMEDKCOMEDK 2015
Options:
  • A $\frac{\pi}{19}$
  • B $-\frac{\pi}{19}$
  • C $\frac{\pi}{2}$
  • D $\frac{\pi}{2}-\frac{\pi}{19}$
Solution:
1739 Upvotes Verified Answer
The correct answer is: $\frac{\pi}{2}$
Let $z=i \sin \frac{\pi}{19}$
or $\quad z=0+i \sin \frac{\pi}{19}$
Let amplitude of $z$ be $\theta$, then
$$
\sin \theta=\frac{\sin \frac{\pi}{19}}{\sqrt{0^{2}+\left(\sin \frac{\pi}{19}\right)^{2}}}\left[\because \sin \theta=\frac{b}{\sqrt{a^{2}+b^{2}}}\right]
$$
or $\sin \theta=\frac{\sin \frac{\pi}{19}}{\sin \frac{\pi}{19}}=1 \Rightarrow \theta=\frac{\pi}{2}$

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