Math Problem Statement

Let Z be a complex number that satisfies the equation Z + i|Z| = 12 + 9i, then what is the value of the imaginary part of Z?

Solution

The equation in the image appears to be:

Z+iZ=12+9iZ + i|Z| = 12 + 9i

where ZZ is a complex number, ii is the imaginary unit, and Z|Z| is the modulus (magnitude) of ZZ.

Let Z=x+yiZ = x + yi, where xx is the real part of ZZ and yy is the imaginary part of ZZ.

We can break this problem into real and imaginary parts:

Step 1: Substitute Z=x+yiZ = x + yi into the equation

The modulus Z|Z| is given by:

Z=x2+y2|Z| = \sqrt{x^2 + y^2}

Substituting Z=x+yiZ = x + yi into the original equation:

(x+yi)+ix2+y2=12+9i(x + yi) + i\sqrt{x^2 + y^2} = 12 + 9i

Step 2: Separate into real and imaginary parts

Now, equate the real and imaginary parts of both sides of the equation:

  • Real part: x=12x = 12

  • Imaginary part: y+x2+y2=9y + \sqrt{x^2 + y^2} = 9

Step 3: Solve for yy

From the real part, we know x=12x = 12. Substitute x=12x = 12 into the equation for the imaginary part:

y+122+y2=9y + \sqrt{12^2 + y^2} = 9 y+144+y2=9y + \sqrt{144 + y^2} = 9

Now solve for yy:

144+y2=9y\sqrt{144 + y^2} = 9 - y Square both sides: 144+y2=(9y)2144 + y^2 = (9 - y)^2 Expand the right-hand side: 144+y2=8118y+y2144 + y^2 = 81 - 18y + y^2 Simplify the equation: 144=8118y144 = 81 - 18y 14481=18y144 - 81 = -18y 63=18y63 = -18y y=6318=72=3.5y = -\frac{63}{18} = -\frac{7}{2} = -3.5

Step 4: Final answer

The imaginary part of ZZ is y=3.5y = -3.5.

Would you like more details or have any questions? Here are some related questions:

  1. What is the modulus of the complex number ZZ?
  2. How do you calculate the argument of a complex number?
  3. Can we verify the solution by substituting back into the original equation?
  4. How is the modulus Z|Z| affected if both the real and imaginary parts change?
  5. What geometric interpretation can be given for complex numbers in this equation?

Tip: When solving complex equations, always separate real and imaginary parts for clearer analysis.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Imaginary Numbers
Modulus of Complex Numbers

Formulas

Z = x + yi
|Z| = sqrt(x^2 + y^2)
Real part equation: x = 12
Imaginary part equation: y + sqrt(x^2 + y^2) = 9

Theorems

Separation of real and imaginary parts in complex numbers

Suitable Grade Level

Grades 10-12