Finding the Locus of z for R: A Real Number

  • Thread starter Thread starter Mentallic
  • Start date Start date
AI Thread Summary
The locus of z defined by z=(1+iR)/(1-iR) for a real number R simplifies to x=(1-R^2)/(1+R^2) and y=(2R)/(1+R^2). Upon calculating the modulus |z|, it is found that |z|=1, indicating that the locus lies on the unit circle in the complex plane. This result suggests that for all real values of R, the points represented by z maintain a constant distance from the origin. The discussion highlights the significance of exploring the modulus to uncover geometric properties of complex functions. Ultimately, the locus of z is confirmed to be the unit circle.
Mentallic
Homework Helper
Messages
3,802
Reaction score
95

Homework Statement


If R is a real number, find the locus of z defined by:

z=\frac{1+iR}{1-iR}

Homework Equations


z=x+iy

The Attempt at a Solution


z=(\frac{1+iR}{1-iR})(\frac{1+iR}{1+iR})

=\frac{1-R^2+i2R}{1+R^2}

Therefore, x=\frac{1-R^2}{1+R^2}

and y=\frac{2R}{1+R^2}

I'm unsure what to do now though...
 
Physics news on Phys.org
Hmmm... why not compute |z| and see if that gives you anything useful:wink:
 
Everything just fell into place and |z|=1. How did you know that would happen? lol
 
I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
Essentially I just have this problem that I'm stuck on, on a sheet about complex numbers: Show that, for ##|r|<1,## $$1+r\cos(x)+r^2\cos(2x)+r^3\cos(3x)...=\frac{1-r\cos(x)}{1-2r\cos(x)+r^2}$$ My first thought was to express it as a geometric series, where the real part of the sum of the series would be the series you see above: $$1+re^{ix}+r^2e^{2ix}+r^3e^{3ix}...$$ The sum of this series is just: $$\frac{(re^{ix})^n-1}{re^{ix} - 1}$$ I'm having some trouble trying to figure out what to...

Similar threads

Back
Top