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Mathematics 7 Online
rvc (rvc):

separate into real and imaginary parts

rvc (rvc):

\[\sin^{-1} (e^{i\theta})\]

rvc (rvc):

\[e^{i\theta}= \sin(x+iy)\]

rvc (rvc):

\[\cos\theta+isin\theta=sinxcos(iy)+cosxsin(iy)\] \[= sinxcoshy+icosxsinhy\]

rvc (rvc):

\[\cos\theta=sinxcoshy~;~\sin\theta=cosxsinhy\]

rvc (rvc):

correct?

OpenStudy (ribhu):

hey

rvc (rvc):

please help nn :)

OpenStudy (ribhu):

can i help? if u want?

rvc (rvc):

yep

rvc (rvc):

please ans

OpenStudy (ribhu):

remember me?

OpenStudy (dinamix):

i think \[\sin^{-1} (\sin(x+iy)) = x+iy\]

OpenStudy (dinamix):

@rvc

OpenStudy (dinamix):

did u see my solution

rvc (rvc):

no its sin inverse e^itheta

rvc (rvc):

@ribhu if u want to help then i dont mind dont ask questions like that

OpenStudy (dinamix):

u didnt mean arcsin or what

rvc (rvc):

\[Let~\sin^{-1} e^{i\theta}=x+iy\]

OpenStudy (dinamix):

cuz i know sin^-1 = arcsin

OpenStudy (irishboy123):

try starting with \[sin z = \frac{e^z - e^{-z}}{2i}\] and note that \[w = arcsin \ e^{i \theta} \implies sin(w) = \ e^{i \theta} =\frac{e^w - e^{-w}}{2i} \] ugly but potentially do-able

rvc (rvc):

hmm what if i go with my steps

rvc (rvc):

@hartnn pls help

OpenStudy (irishboy123):

you steps are technically correct, i believe. where are you taking it from here?

rvc (rvc):

i need the value of x and y

OpenStudy (irishboy123):

well i found a reliable formula \[arcsin z = -i \ ln (iz \pm \sqrt{1-z^2})\] and the answer i get from the method i propose actually looks very similar i do not see where you go next in you approach though i see no problems with it

OpenStudy (irishboy123):

following on: \(2i e^{i \theta } = e^w - e^{-w}\) \(i = e^{\pi/2}\) \(u = e^w\) \(u - 2 e^{i(\theta + \pi/2)} - \frac{1}{u} = 0\) \(u^2 - u.2 e^{i(\theta + \pi/2)} - 1 = 0\) and apply quadratic formula => gets you that really ugly formula i posted above

OpenStudy (irishboy123):

the switch to \(e^{i(\theta + \pi /2 )}\) is OTT and only complicates matters. you can just stuff it all straight into the quadratic mea culpa :-(

rvc (rvc):

@hartnn @baru @IrishBoy123 can we get back to this question please..

OpenStudy (baru):

i dont even understand how to interpret that, sin( complex number) is a thing ?

OpenStudy (baru):

i think these are @ParthKohli 's hunting grounds

rvc (rvc):

@Kainui

rvc (rvc):

@hartnn please help whenever u r online...

OpenStudy (kainui):

$$z= \frac{z+z^*}{2} + i \frac{z-z^*}{2i} = \Re(z)+i \Im(z)$$ That's probably the most important formula you can have, try it out on anything simple to test it.

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