Math Problem Statement

Determine the geometric locus of the complex numbers z that satisfy the given conditions: Arg(z) = 3π/4, Arg(z - 2 + 2i) = 3π/4, Arg(z + 2 - 2i) = 3π/4, and Arg(z - 2 + 2i) = π/4.

Solution

The problem involves determining the geometric locus of complex numbers zz that satisfy given conditions for the arguments of specific complex transformations. Here's a breakdown:


Step 1: Understanding the Problem

  • The argument of a complex number z=x+yiz = x + yi is defined as the angle θ\theta that the vector from the origin to zz makes with the positive real axis in the complex plane.

  • The conditions in this problem require determining the geometric place where the arguments (angles) of the transformed versions of zz are constant. Specifically, the argument conditions are:

    • Arg(z)=3π4\text{Arg}(z) = \frac{3\pi}{4}
    • Arg(z2+2i)=3π4\text{Arg}(z - 2 + 2i) = \frac{3\pi}{4}
    • Arg(z+22i)=3π4\text{Arg}(z + 2 - 2i) = \frac{3\pi}{4}
    • Arg(z2+2i)=π4\text{Arg}(z - 2 + 2i) = \frac{\pi}{4}

Step 2: Interpretation of Each Condition

  1. Arg(z)=3π4\text{Arg}(z) = \frac{3\pi}{4}:

    • The argument 3π4\frac{3\pi}{4} corresponds to a line making a 135135^\circ angle (or 3π4\frac{3\pi}{4}) with the positive real axis.
    • This is the line passing through the origin and having a slope of 1-1.
  2. Arg(z2+2i)=3π4\text{Arg}(z - 2 + 2i) = \frac{3\pi}{4}:

    • The term z(22i)z - (2 - 2i) represents a translation of zz by (2,2)(2, -2).
    • The line Arg(z2+2i)=3π4\text{Arg}(z - 2 + 2i) = \frac{3\pi}{4} is parallel to the line Arg(z)=3π4\text{Arg}(z) = \frac{3\pi}{4} but shifted such that it passes through (2,2)(2, -2).
  3. Arg(z+22i)=3π4\text{Arg}(z + 2 - 2i) = \frac{3\pi}{4}:

    • Here z+(22i)z + (2 - 2i) translates zz by (2,2)(-2, 2).
    • The line is again parallel to the original line Arg(z)=3π4\text{Arg}(z) = \frac{3\pi}{4} but shifted to pass through (2,2)(-2, 2).
  4. Arg(z2+2i)=π4\text{Arg}(z - 2 + 2i) = \frac{\pi}{4}:

    • This line corresponds to an angle of π4\frac{\pi}{4} or 4545^\circ with the positive real axis.
    • The line passes through (2,2)(2, -2) and has a slope of 11.

Step 3: Final Observations

  • Each condition describes a straight line in the complex plane:

    • Lines with Arg=3π4\text{Arg} = \frac{3\pi}{4} have a slope of 1-1.
    • Lines with Arg=π4\text{Arg} = \frac{\pi}{4} have a slope of 11.
  • The shifts (2,2)(2, -2) and (2,2)(-2, 2) correspond to translations of the original lines.

Thus, the problem defines geometric loci that are straight lines shifted to specific points.


Do you need a visual explanation or step-by-step verification of each case? Let me know!


Related Questions to Explore:

  1. What is the geometric interpretation of the argument of a complex number?
  2. How do translations affect the argument of a complex number?
  3. What is the slope of a line corresponding to a given argument θ\theta?
  4. How can complex number transformations be represented geometrically?
  5. How do you derive the equation of a line from its argument and a point?

Tip: The argument of a complex number z=x+yiz = x + yi can be found using tan1(y/x)\tan^{-1}(y/x), keeping track of the quadrant where zz lies.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Arguments of Complex Numbers
Geometric Locus

Formulas

Argument of a complex number z = x + yi: θ = tan⁻¹(y / x)
Slope of a line corresponding to Arg(z) = θ: slope = tan(θ)

Theorems

Geometric representation of Arg(z) as the angle a complex number makes with the positive real axis
Translation of complex numbers in the complex plane

Suitable Grade Level

Undergraduate Level (Complex Analysis or Advanced Algebra)