Math Problem Statement

Determine the real part, imaginary part, conjugate, modulus, and argument of the complex number a = -1 + 3i.

Solution

Let's solve this step by step for the given complex numbers a=1+3ia = -1 + 3i and b=1ib = -1 - i.

Questions to solve:

  1. Re(a)\text{Re}(a): The real part of aa.
  2. Im(a)\text{Im}(a): The imaginary part of aa.
  3. a\overline{a}: The conjugate of aa.
  4. a|a|: The modulus of aa.
  5. arg(a)\arg(a): The argument of aa.

Solution:

  1. Real part of aa: Re(a)=1\text{Re}(a) = -1

  2. Imaginary part of aa: Im(a)=3\text{Im}(a) = 3

  3. Conjugate of aa: The conjugate of a complex number a=x+yia = x + yi is a=xyi\overline{a} = x - yi. a=13i\overline{a} = -1 - 3i

  4. Modulus of aa: The modulus of a complex number a=x+yia = x + yi is given by: a=x2+y2|a| = \sqrt{x^2 + y^2} Substituting x=1x = -1 and y=3y = 3: a=(1)2+32=1+9=10|a| = \sqrt{(-1)^2 + 3^2} = \sqrt{1 + 9} = \sqrt{10}

  5. Argument of aa: The argument arg(a)\arg(a) of a complex number a=x+yia = x + yi is given by: arg(a)=tan1(yx)\arg(a) = \tan^{-1}\left(\frac{y}{x}\right) For a=1+3ia = -1 + 3i, x=1x = -1 and y=3y = 3: arg(a)=tan1(31)\arg(a) = \tan^{-1}\left(\frac{3}{-1}\right) This simplifies to: arg(a)=tan1(3)\arg(a) = \tan^{-1}(-3) Since the complex number lies in the second quadrant (negative real, positive imaginary), we adjust the angle to: arg(a)=πtan1(3)\arg(a) = \pi - |\tan^{-1}(3)| Numerically, arg(a)2.82radians.\arg(a) \approx 2.82 \, \text{radians}.


Summary:

  • Re(a)=1\text{Re}(a) = -1
  • Im(a)=3\text{Im}(a) = 3
  • a=13i\overline{a} = -1 - 3i
  • a=10|a| = \sqrt{10}
  • arg(a)2.82radians\arg(a) \approx 2.82 \, \text{radians}

Would you like to confirm these calculations or solve for bb as well?

Follow-Up Questions:

  1. How would the modulus of bb differ from aa?
  2. What is the graphical interpretation of arg(a)\arg(a) on the complex plane?
  3. Can you verify the conjugate property aa=a2a \cdot \overline{a} = |a|^2?
  4. How does changing the sign of the imaginary part affect arg(a)\arg(a)?
  5. What happens to the modulus if both real and imaginary parts are doubled?

Tip:

Always remember that arguments of complex numbers are calculated with respect to their quadrant position!

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Real and Imaginary Parts
Modulus
Argument
Conjugates

Formulas

Re(z): Real part of z
Im(z): Imaginary part of z
Conjugate: \( \overline{z} = x - yi \)
Modulus: \( |z| = \sqrt{x^2 + y^2} \)
Argument: \( \arg(z) = \tan^{-1}(y/x) \), adjusted by quadrant

Theorems

Polar representation of complex numbers
Pythagoras theorem for modulus

Suitable Grade Level

Grades 10-12