Mathematics
Grade 11
15 min
Divide complex numbers
Divide complex numbers
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define the complex conjugate and find the conjugate of any given complex number.
Explain why multiplying by the complex conjugate is the key step in dividing complex numbers.
Divide a complex number by a pure imaginary number.
Divide any two complex numbers in the form a + bi.
Simplify the result of complex division into the standard form a + bi.
Verify the result of a complex division problem through multiplication.
How can you possibly 'divide' by a number that includes the square root of -1? 🤔 It's like trying to rationalize a denominator, but with an imaginary twist!
This tutorial will guide you through the process of dividing complex numbers. You will learn about a special tool called the 'complex conjugate' that transforms...
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Key Concepts & Vocabulary
TermDefinitionExample
Complex Number (Standard Form)A number written in the form a + bi, where 'a' is the real part and 'b' is the imaginary part. 'i' is the imaginary unit.The number 5 - 2i is a complex number with a real part of 5 and an imaginary part of -2.
Imaginary Unit (i)The number defined by the property i² = -1. It is the foundation of imaginary and complex numbers.√(-9) = √(9 * -1) = √9 * √(-1) = 3i
Complex ConjugateFor a complex number a + bi, its complex conjugate is a - bi. You simply change the sign of the imaginary part.The complex conjugate of 4 + 7i is 4 - 7i. The conjugate of -2 - 3i is -2 + 3i.
DenominatorIn a fraction, the number or expression on the bottom, by which the numerator is being divided.In the expression (3 + i) / (1 - 2i), the...
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Core Formulas
The Complex Conjugate
If z = a + bi, then its conjugate is z̄ = a - bi.
This is used to create a real number in the denominator. To find the conjugate, you only change the sign of the imaginary term.
Product of Conjugates
(a + bi)(a - bi) = a² + b²
When you multiply a complex number by its conjugate, the result is always a non-negative real number. This is the key to eliminating 'i' from the denominator.
The Division Algorithm
\frac{a + bi}{c + di} = \frac{a + bi}{c + di} \cdot \frac{c - di}{c - di} = \frac{(a + bi)(c - di)}{c^2 + d^2}
To divide complex numbers, multiply the numerator and the denominator by the conjugate of the denominator. Then, simplify the resulting expression into standard form.
4 more steps in this tutorial
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Sign Up Free to ContinueSample Practice Questions
Challenging
Find the complex number z = x + yi that satisfies the equation z(1 + 2i) = 5 + 5i.
A.3 - i
B.3 + i
C.1 - 3i
D.1 + 3i
Challenging
What is the multiplicative inverse (reciprocal) of 2 - 3i?
A.2 + 3i
B.2/13 + 3/13 i
C.1/2 - 1/3 i
D.-2 + 3i
Challenging
Let w = (5 + i) / (1 - 3i). What is the complex conjugate of w?
A.1/5 - 8/5 i
B.1/5 + 8/5 i
C.1/5 + 4/5 i
D.1/5 - 4/5 i
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