Thursday, October 23, 2014

sinz=z , z=x+iy

sin w=z
sin
w=((e^{iw}-e^{iw})/(2i))
e^{iw}-e^{-iw}=2iz   multiply everything by
e^{iw}
e^{2iw}-1=2ize^{iw}
e^{2iw}-2ize^{iw}-1=0
y=e^{iw}
y²-2izy-1=0
y=((2iz±√((-2iz)²-4(-1)))/2)=((-iz±√(-4z²+4))/2)
e^{iw}=-iz±√(1-z²)  
so our answer
is
iw=ln(-iz±√(1-z²))
w=(1/i)ln(-iz±√(1-z²))+2πn


I
do not see an easy way to solve this equation for z.


z=0 is
an obvious solution.


Using newton's method on the original
function


f(z) = sin(z)-z


f
'(z) = cos(z) - 1


Pick a x_0 and iterate the following
formula


x_(n+1) = x_n - f(x_n)/f
'(x_n)


I get z = 7.4976763 - 2.7686783 i as one posible
answer from about 10 iterations starting with (5+5i)


z =
13.899960 - 3.3522099 i  is another answer.


I do not see a
pattern, but perhaps you can...

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