If z is a complex number such that z + 1 + i = |z|, then.

Question image

Understand the Problem

The question is asking to analyze the complex number z based on the equation provided, where z is related to its magnitude and argument. We need to find the correct properties of z given the condition z + 1 + i = |z|.

Answer

$|z| = \frac{1}{2}$; $\arg(z) = \pi$
Answer for screen readers

The values derived are:

  • ( |z| = \frac{1}{2} )
  • ( \arg(z) = \pi )

Steps to Solve

  1. Rewrite the equation in terms of z The given equation is ( z + 1 + i = |z| ). We can rewrite this as: $$ |z| = z + 1 + i $$

  2. Express z in terms of its components Let ( z = x + yi ), where ( x ) is the real part and ( y ) is the imaginary part. Then: $$ |z| = \sqrt{x^2 + y^2} $$ Substituting, we have: $$ \sqrt{x^2 + y^2} = (x + 1) + yi $$

  3. Separate real and imaginary parts From the equation, we break it into real and imaginary parts:

    • Real part: ( \sqrt{x^2 + y^2} = x + 1 )
    • Imaginary part: ( 0 = y )
  4. Find the values of components Since ( y = 0 ), it follows that ( z = x ) (a real number). The magnitude simplifies to: $$ |z| = |x| $$ Thus, the equation simplifies to: $$ |x| = x + 1 $$

  5. Solve for x We can now solve the equation:

    • Case 1: ( x \geq 0 ) gives ( x = x + 1 ), which is a contradiction.
    • Case 2: ( x < 0 ) gives ( -x = x + 1 ) or ( -2x = 1 ). Solving for ( x ) gives: $$ x = -\frac{1}{2} $$ So, ( z = -\frac{1}{2} ).
  6. Find the magnitude and argument The magnitude is: $$ |z| = \left| -\frac{1}{2} \right| = \frac{1}{2} $$ The argument, since ( z ) is negative on the real axis, is: $$ \arg(z) = \pi \text{ (or } 180^\circ\text{)} $$

The values derived are:

  • ( |z| = \frac{1}{2} )
  • ( \arg(z) = \pi )

More Information

The magnitude ( |z| ) indicates the distance from the origin in the complex plane, while the argument ( \arg(z) ) shows the angle with respect to the positive real axis. Since we found that ( z ) lies on the negative real axis, its argument reflects that position.

Tips

  • Confusing the cases for ( |z| = x + 1 ): It's important to check both the positive and negative scenarios.
  • Mixing up the imaginary components: Ensure that you clearly separate real and imaginary parts when solving.

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