Complex Numbers

Definition

Complex numbers are a numerical system that extends the real number system to include imaginary numbers. They are represented in the form $a + bi$, where $a$ is the real part and $b$ is the imaginary part, and $i$ represents the square root of -1.

5 Must Know Facts For Your Next Test

1. Complex numbers are used to represent quantities that have both magnitude and direction, such as in electrical engineering and quantum mechanics.
2. The set of complex numbers, denoted by $\mathbb{C}$, includes all numbers of the form $a + bi$, where $a$ and $b$ are real numbers.
3. Complex numbers can be added, subtracted, multiplied, and divided, following specific rules and operations.
4. The modulus (or absolute value) of a complex number $a + bi$ is defined as $\sqrt{a^2 + b^2}$, which represents the distance from the origin to the point on the complex plane.
5. The conjugate of a complex number is used to divide complex numbers, as well as to find the modulus and argument (or phase) of a complex number.

Review Questions

• Explain how complex numbers can be used to divide radical expressions.
  • Complex numbers can be used to divide radical expressions by first expressing the radicand as a complex number. For example, to divide $\sqrt{9 - 4i}$, we can rewrite the radicand as $9 - 4i$, a complex number. To divide this by a real number, we can use the conjugate of the complex number, which is $9 + 4i$. Multiplying the original expression by the conjugate and simplifying the result will give the final answer in the form $a + bi$, where $a$ and $b$ are real numbers.
• Describe how the complex number system is used in the context of 8.8 'Use the Complex Number System'.
  • The complex number system is essential in the context of 8.8 'Use the Complex Number System' because it allows for the representation and manipulation of quantities that have both magnitude and direction, such as in electrical engineering and quantum mechanics. Complex numbers can be used to perform operations like addition, subtraction, multiplication, and division, as well as to find the modulus and argument of a complex number. Understanding the properties and operations of complex numbers is crucial for solving problems involving the complex number system.
• Analyze how the concept of conjugates is used in the context of complex numbers.
  • The concept of conjugates is an important tool in working with complex numbers. The conjugate of a complex number $a + bi$ is $a - bi$, which is obtained by changing the sign of the imaginary part. Conjugates are used to divide complex numbers, as well as to find the modulus and argument of a complex number. When dividing complex numbers, multiplying the numerator and denominator by the conjugate of the denominator can simplify the calculation and produce a result in the form $a + bi$, where $a$ and $b$ are real numbers. Additionally, the modulus of a complex number is equal to the square root of the sum of the squares of the real and imaginary parts, which can be calculated using the conjugate. Understanding the properties and applications of conjugates is crucial for working with complex numbers in the context of 8.8 'Use the Complex Number System'.

Related terms

Imaginary Number: An imaginary number is a number that, when multiplied by itself, results in a negative number. The symbol $i$ is used to represent the imaginary unit, where $i^2 = -1.

Real Number: A real number is a number that can be represented on the number line, including positive and negative integers, fractions, and irrational numbers.

Conjugate:

The conjugate of a complex number $a + bi$ is $a - bi$, which is obtained by changing the sign of the imaginary part.