Checking the answer to complex number question

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SUMMARY

The discussion focuses on finding an equation connecting the real part (x) and the imaginary part (y) of a complex number z, specifically for the expression (z-1)/(z+1) to have a defined argument α. The solution involves substituting z with x + iy, leading to the equation tan(α) = 2y / (x² + y² - 1). Participants suggest simplifying the result into the standard form of a circle, represented as (x² + (y-a)² = b²), for clarity and ease of interpretation.

PREREQUISITES
  • Understanding of complex numbers and their representation (z = x + iy).
  • Familiarity with the concept of argument in complex analysis (arg(z) = tan⁻¹(y/x)).
  • Knowledge of algebraic manipulation of complex fractions.
  • Basic understanding of the geometric representation of circles in the Cartesian plane.
NEXT STEPS
  • Learn how to derive the argument of complex functions using polar coordinates.
  • Study the geometric interpretation of complex numbers and their transformations.
  • Explore the properties of circles in the complex plane and their equations.
  • Investigate the relationship between complex functions and their graphical representations.
USEFUL FOR

Students studying complex analysis, mathematicians interested in geometric interpretations, and educators teaching algebraic manipulation of complex numbers.

rock.freak667
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Homework Statement


Find an equation connecting x and y for which (z-1)/(z+1) has an argument [itex]\alpha[/itex]


Homework Equations


z=x+iy

arg(z)=tan-1(y/x)


The Attempt at a Solution



[tex]\frac{z-1}{z+1}[/tex]

Substituting z=x+iy

[tex]\Rightarrow \frac{z-1}{z+1}=\frac{(x-1)+iy}{(x+1)+iy}[/tex]

Realizing

[tex]\frac{(x+1)(x-1)+iy(x+1)-iy(x-1)-i^2y^2}{(x+1)^2+y^2}[/tex]

Re:i2=-1

[tex]= \frac{x^2+y^2-1}{(x+1)^2+y^2} +i \frac{2y}{(x+1)^2+y^2}[/tex]

Thus

[tex]tan\alpha = \frac{2y}{x^2+y^2-1}[/tex]

Is this correct? Or should I just put in the form of a circle?
 
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rock.freak667 said:
Find an equation connecting x and y for which (z-1)/(z+1) has an argument [itex]\alpha[/itex]

Thus

[tex]tan\alpha = \frac{2y}{x^2+y^2-1}[/tex]

Is this correct? Or should I just put in the form of a circle

Hi rock.freak667! :smile:

Yes, that's messy! :biggrin:

Definitely put it in the form of a nice circle (x² + (y-a)² = b²)! :wink:
 

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