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Let $z$ and $w$ be the complex numbers in the picture below:

If $|z| = 4$ and $|w| = 2$, then what is the imaginary part of $\dfrac{z}{w}$?​

 Jan 12, 2019
 #1
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ok just like the other one i did, the angle is 45 degrees. ignoring the diagram(again lol)

 

 

z=a+bi

w=c+di

 

a^2+b^2=16

c^2+d^2=4

 

if z=-4i then w is -2sqrt2-2isqrt2

 

divide w/z and take the reciprocal.

 

w/z = i(-2sqrt2-2isqrt2)/4 or (2sqrt2-2isqrt2)/4 which reduces to (sqrt2-isqrt2)/2.

 

to get z/w you have to take the reciprocal which is 2/(sqrt2-isqrt2). multiply by conjugate on top and bottom you get 2(sqrt2+isqrt2)/(2+2), which is

(sqrt2+isqrt2)/2 so the imaginary part is sqrt2/2.

 

 

 

HOPE THIS HELPED!!

 Jan 12, 2019
 #2
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Sorry is wrong i dont know answer online

Guest Jan 12, 2019
edited by Guest  Jan 12, 2019
 #3
avatar+118702 
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If $|z| = 4$ and $|w| = 2$, then what is the imaginary part of $\dfrac{z}{w}$?​

 

w=2eiθz=4ei(θ+π4) zw=4ei(θ+π4)2eiθ=2eiθ+πi4iθ=2eπi4=2cosπ4+(2sinπ4)i=22+22i=2+2i

 

 

So the imaginary part is    2i

 Jan 12, 2019

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