Complex Numbers Simplification and Operations

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Questions and Answers

Simplify $3(1 - 2i)$.

-3 + 6i

Simplify $(2 + 3i)(4 - 5i)$.

23 + 2i

Express $(4 - 3i)^3$ in the form (a + ib).

-44 - 117i

If $z = (\sqrt{2} - \sqrt{3}i)$, find Re(z), Im(z), \bar{z} and |z|.

<p>Re(z) = \sqrt{2}, Im(z) = -\sqrt{3}, \bar{z} = \sqrt{2} + \sqrt{3}i, |z| = \sqrt{5}</p> Signup and view all the answers

Write down the conjugate of (i) $-3 + \sqrt{-1}$ (ii) $i^3$

<p>(i) -3 - i, (ii) -i</p> Signup and view all the answers

Find the modulus of $|\frac{1 + i}{1 - i} - \frac{1 - i}{1 + i}|$

<p>2</p> Signup and view all the answers

If $z_1 = (1 - i) $ and $z_2 = (-2 + 4i)$, find Im$\left(\frac{z_1z_2}{z_1}\right)$.

<p>-4</p> Signup and view all the answers

Find the least positive integral value of $m$ for which $\left( \frac{1 + i}{1 - i} \right)^m$ = 1.

<p>m = 4</p> Signup and view all the answers

Find the value of $x$ and $y$, if (i) $2 + (x + iy) = (3 - i)$ (ii) $x + 4iy = ix + y + 3$

<p>(i) x = 1, y = -2, (ii) x = 4, y = 1</p> Signup and view all the answers

Show that $\left(\frac{\sqrt{7} + i\sqrt{3}}{\sqrt{7} - i\sqrt{3}} + \frac{\sqrt{7} - i\sqrt{3}}{\sqrt{7} + i\sqrt{3}}\right)$ is real.

<p>The expression simplifies to $\frac{14}{4}$ which is real.</p> Signup and view all the answers

Find real values of $\theta$ for which $\left(\frac{3 + 2isin\theta}{1 - 2isin \theta}\right)$ is purely real.

<p>$\theta = 0$</p> Signup and view all the answers

If (x + iy) = $\frac{(a + ib)}{(a - ib)}$, prove that $(x^2 + y^2) = 1$.

<p>The given equation can be rewritten as $(x + iy)(a - ib) = (a + ib)$. Expanding both sides gives us a system of equations, yielding an equation that implies $(x^2 + y^2) = 1$.</p> Signup and view all the answers

If z = (x + iy) and w = $\frac{1 - iz}{z - i}$ such that |w| = 1, then show that z is purely real.

<p>Using the given information, we can substitute the expression for w and solve for z, ultimately showing that the imaginary part of z is zero, thereby proving that z is purely real.</p> Signup and view all the answers

Flashcards

Complex Number Form

A complex number expressed as a + bi, where a, b are real numbers and i is the imaginary unit.

Conjugate of a Complex Number

For a complex number a + bi, its conjugate is a - bi.

Modulus of a Complex Number

The modulus |z| of a complex number z = a + bi is calculated as √(a² + b²).

Real Part of a Complex Number

The real part of a complex number z = a + bi is the value a.

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Imaginary Part of a Complex Number

The imaginary part of a complex number z = a + bi is the value b.

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Multiplying Complex Numbers

To multiply (a + bi) by (c + di), use (ac - bd) + (ad + bc)i.

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Dividing Complex Numbers

To divide (a + bi) by (c + di), multiply numerator and denominator by the conjugate of the denominator.

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Purely Real Complex Number

A complex number z is purely real if its imaginary part is zero (b = 0).

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Purely Imaginary Complex Number

A complex number z is purely imaginary if its real part is zero (a = 0).

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Complex Numbers Addition

To add complex numbers (a + bi) and (c + di), sum real parts and imaginary parts separately.

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Exponentiation of Complex Numbers

Raising a complex number to a power involves repeated multiplication of its form.

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Real Values from Complex Expressions

Finding real values of an expression often means setting its imaginary part to zero.

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Least Positive Integral Value

The smallest positive integer that satisfies an equation or condition.

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Complex Number Equalities

Equal complex numbers have both real parts equal and imaginary parts equal.

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Complex Number Inequalities

Inequalities for complex numbers often relate to the modulus or real/imaginary parts.

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Expression Simplification

Transforming complex expressions into simpler or standard forms like a + bi.

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Finding Imaginary Component

Determining the imaginary part of a complex quotient involves isolating the term with 'i'.

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Real Values from Sinusoidal Functions

When involving sin θ, find conditions when sin θ makes an expression real.

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Complex Modulus Simplification

Simplifying a fraction of complex numbers to find modulus is done using conjugates.

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Study Notes

Complex Numbers Simplification and Operations

  • Simplify complex numbers of the form (a + bi) involving multiplication, addition, subtraction, and powers.
  • Example: 3(1 - 2i) - (-4 - 5i) + (-8 + 3i) = -9 + 4i
  • Example: (2+3i)(4-5i) = 23 - 7i

Complex Number Representation

  • Express complex numbers in different forms (rectangular, polar, exponential).
  • Express complex numbers in the form a + bi where a and b are real numbers.
  • Example (4 - 3i)³ can be expressed in a + bi form.

Conjugates

  • Find the complex conjugate of a complex number.
  • The conjugate of a + bi is a - bi.
  • Example: Conjugate of (-3 + √−1) = (-3 - i)
  • Example: Conjugate of i³ is -i

Modulus of a Complex Number

  • Calculate the modulus (absolute value) of a complex number.
  • |z| = √(x² + y²) where z = x + yi.
  • Example: | √2 + i√3 | = √5
  • Calculate the modulus of (1 + i) / (1 - i) = √2, which is the magnitude of the complex number.

Operations with Complex Numbers

  • Calculate the real and imaginary parts of a complex number.
  • Re(√2 - √-3) = √2, Im(√2 - √-3) = - √3
  • Find the sum and difference of complex numbers.
  • Find the product and quotient of complex numbers.
  • Example: If z₁ = 1 - i and z₂ = -2 + 4i, find Im(z₁z₂/z₁) = 1
  • Calculate (z₁z₂)/z₁

Solving for Integer Values

  • Determine the least positive integer value of m that satisfies equation for a complex number.
  • Example: Find m if (1 + i)^(m) / (1 − i)^(m) = 1
  • Answer for this example is m = 4

Real Parts and Imaginary Parts

  • Determine values of x and y using equations involving complex numbers.
  • Example: if 2 + (x + yi) = 3 - i, then x = 1 and y = -1
  • Example equations: x + 4iy = ix + y + 3

Real Numbers from Complex Number Operations

  • Determine complex number expressions which simplify to real numbers.
  • Show expressions such as (√7 + i√3) / (√7 − i√3) + (√7 − i√3) / (√7 + i√3) that are real.

Prove Equality of Expressions

  • Prove an algebraic equality involving complex values such as (x² + y²) = 1
  • if (x + iy) = (a + i b)/(a - i b).

Complex Numbers and Modulus

  • If | w | = 1 and w = (1 - iz) / (z - i), show that z is purely real.

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