Problem 35 - Precalculus : Building Concepts and Connections

Question

Find the complex conjugate of each number. $$i^{2}$$

Step-by-Step Solution

Answer

The complex conjugate of \(i^{2}\) is -1.

Step 1: Simplify the Power of i

The value of \(i^{2}\) is defined as -1. So, the given complex number is -1.

Step 2: Write in the form of a Complex Number

We can write -1 in the form of a complex number as -1 + 0i.

Step 3: Find the Complex Conjugate

The complex conjugate of a complex number \(a + bi\) is \(a - bi\). So, the complex conjugate of -1 + 0i is -1 - 0i, which is simply -1.

Key Concepts

Imaginary Numbers

Imaginary numbers are an extension of the real numbers and provide solutions to equations that have no solution in the realm of real numbers. In essence, an imaginary number is defined as a multiple of the imaginary unit, denoted as 'i', where i is the square root of -1. This concept is fundamental, as it allows us to solve equations like \( x^2 + 1 = 0 \), which results in \( x = \pm i \).

While real numbers can be thought of as points on a horizontal line, imaginary numbers can be visualized on a perpendicular axis, creating a two-dimensional number system alongside the real numbers. It's crucial to recognize that imaginary numbers are not 'imaginary' in the sense of being unreal or made-up; they are simply numbers that have different properties from the real numbers we use for counting or measuring.

Powers of i

The powers of the imaginary unit 'i' follow a cyclical pattern, which can be quite handy when simplifying expressions involving these. Starting from the definition, \( i^1 = i \), and by knowing that \( i^2 = -1 \), we can deduce further powers. For instance, \( i^3 = i^2 \times i = -1 \times i = -i \), and \( i^4 = (i^2)^2 = (-1)^2 = 1 \).

Cyclical Nature of i

Every fourth power of i repeats the sequence: \( i, -1, -i, 1 \). So for any power of i, we can reduce it by finding the remainder when that power is divided by 4. This is a critical simplification tactic when dealing with powers of i in complex numbers.

• \( i^5 = i \) (since \( 5 \mod 4 = 1 \))
• \( i^6 = -1 \) (since \( 6 \mod 4 = 2 \))

Understanding this repetition allows for the quick evaluation of higher powers of i, as demonstrated in the given exercise.

Complex Numbers

Complex numbers are numbers that comprise a real part and an imaginary part, usually expressed in the form \( a + bi \), where 'a' is the real part, 'b' is the imaginary part, and 'i' is the imaginary unit. They are represented as points or vectors in the complex plane, with the real part corresponding to the x-coordinate and the imaginary part to the y-coordinate.

A key operation with complex numbers is finding the complex conjugate, which involves reversing the sign of the imaginary part. For example, the complex conjugate of \( a + bi \) is \( a - bi \). This operation has many applications, including simplifying the division of complex numbers and finding the modulus or absolute value of a complex number.

Applying the Concept

In the exercise provided, we consider the complex number -1, which can be expressed as \(-1 + 0i\). Its complex conjugate is thus \(-1 - 0i\), which simplifies to just -1, since the imaginary part is zero. This step is fundamental in managing complex operations and understanding the symmetrical relationship between a complex number and its conjugate.