Math Problem Statement

Consider a non-zero complex number z satisfying the equation: Re(z + z̅ + |z|) / Im(z - z̅ - i|z|) = 1, where i = √-1. The set of exhaustive values of arg(z) is?

Solution

We are given the equation involving a non-zero complex number zz which satisfies:

Re(z+zˉ+z)Im(zzˉiz)=1,\frac{\text{Re}\left(z + \bar{z} + |z|\right)}{\text{Im}\left(z - \bar{z} - i |z|\right)} = 1, where i=1i = \sqrt{-1} is the imaginary unit and zˉ\bar{z} denotes the complex conjugate of zz.

Step-by-step Analysis:

Let z=x+iyz = x + iy where xx and yy are the real and imaginary parts of zz, respectively. Therefore, the following holds:

  • zˉ=xiy\bar{z} = x - iy (complex conjugate of zz),
  • z=x2+y2|z| = \sqrt{x^2 + y^2} (modulus of zz).

Substitute these into the equation:

1. Real part:

Re(z+zˉ+z)=Re(x+iy+xiy+z)=Re(2x+z).\text{Re}(z + \bar{z} + |z|) = \text{Re}(x + iy + x - iy + |z|) = \text{Re}(2x + |z|). Thus, the real part is: 2x+z=2x+x2+y2.2x + |z| = 2x + \sqrt{x^2 + y^2}.

2. Imaginary part:

Im(zzˉiz)=Im(x+iy(xiy)iz)=Im(2iyiz)=2yz.\text{Im}(z - \bar{z} - i|z|) = \text{Im}(x + iy - (x - iy) - i|z|) = \text{Im}(2iy - i|z|) = 2y - |z|.

3. Equation:

Substitute these expressions into the original equation:

2x+x2+y22yx2+y2=1.\frac{2x + \sqrt{x^2 + y^2}}{2y - \sqrt{x^2 + y^2}} = 1.

4. Solving the equation:

Cross-multiply to get: 2x+x2+y2=2yx2+y2.2x + \sqrt{x^2 + y^2} = 2y - \sqrt{x^2 + y^2}.

Move terms involving x2+y2\sqrt{x^2 + y^2} to one side: 2x+x2+y2+x2+y2=2y,2x + \sqrt{x^2 + y^2} + \sqrt{x^2 + y^2} = 2y, 2x+2x2+y2=2y,2x + 2\sqrt{x^2 + y^2} = 2y, x+x2+y2=y.x + \sqrt{x^2 + y^2} = y.

Square both sides to eliminate the square root: (x+x2+y2)2=y2,\left(x + \sqrt{x^2 + y^2}\right)^2 = y^2, x2+2xx2+y2+x2+y2=y2.x^2 + 2x\sqrt{x^2 + y^2} + x^2 + y^2 = y^2. Simplify: 2x2+2xx2+y2=0.2x^2 + 2x\sqrt{x^2 + y^2} = 0. Thus, x(x+x2+y2)=0.x(x + \sqrt{x^2 + y^2}) = 0.

This gives us two cases:

  1. x=0x = 0,
  2. x+x2+y2=0x + \sqrt{x^2 + y^2} = 0.

Case 1: x=0x = 0

If x=0x = 0, the equation reduces to: 0+02+y2=yy=y,0 + \sqrt{0^2 + y^2} = y \quad \Rightarrow \quad y = y, so no restriction on yy. Hence, z=iyz = iy is purely imaginary.

Case 2: x+x2+y2=0x + \sqrt{x^2 + y^2} = 0

This implies: x2+y2=x.\sqrt{x^2 + y^2} = -x. However, since x2+y20\sqrt{x^2 + y^2} \geq 0, this case does not give valid solutions.

Conclusion:

The set of exhaustive values of arg(z)\arg(z) (argument of zz) is π2\frac{\pi}{2} or 3π2\frac{3\pi}{2}, meaning that zz lies on the imaginary axis. Therefore, zz is purely imaginary.

Do you have any questions or need further details?


Related questions:

  1. What is the geometrical interpretation of the argument of a complex number?
  2. How does the modulus of a complex number influence its properties?
  3. How can complex conjugates help in solving equations involving complex numbers?
  4. What role does the imaginary unit ii play in complex number calculations?
  5. How does the polar form of a complex number simplify the calculation of arguments?

Tip: When solving complex number equations, expressing the complex number in terms of real and imaginary parts can significantly simplify the solution process.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Argument of Complex Numbers
Complex Conjugate

Formulas

z = x + iy (where x and y are real and imaginary parts)
z̅ = x - iy (complex conjugate of z)
|z| = √(x² + y²) (modulus of z)
arg(z) = argument of the complex number z

Theorems

Properties of Complex Numbers
Complex Conjugate Theorem
Modulus and Argument Relationship

Suitable Grade Level

Grades 11-12 (Senior High School)