Problem 16 - College Algebra and Calculus: An Applied Approach

Question

Write the complex number in standard form and find its complex conjugate. $$(-i)^{3}$$

Step-by-Step Solution

Answer

The standard form of \(-i^3\) is \(0 - 1i\) and its complex conjugate is \(i\).

Step 1: Simplify the imaginary unit power

Start by solving \((-i)^3\). The power of 3 tells to multiply -i with itself three times: \((-i)*(-i)*(-i)\) = -i. So the complex number is -i.

Step 2: Write in standard form

The standard form for complex numbers is \(a + bi\), where \(a\) and \(b\) are real numbers. Write -i in the standard form. Here, \(a=0\) and \(b=-1\). So the standard form of the given complex number is \(0 - 1i\).

Step 3: Find the complex conjugate

The complex conjugate of a complex number \(a + bi\) is \(a - bi\). In terms of the standard form (0 - 1i), the complex conjugate is obtained by changing the sign of the imaginary part. So, the complex conjugate is \(0 + 1i\) or simply \(i\).

Key Concepts

Imaginary Unit

The imaginary unit, denoted as \(i\), is a fundamental concept in the study of complex numbers. It is defined as the square root of -1, i.e., \(i^2 = -1\). This unique property allows \(i\) to represent quantities that cannot be expressed as real numbers alone. Imaginary numbers, when combined with real numbers, form complex numbers.
Complex numbers are typically in the form \(a + bi\), where \(a\) and \(b\) are real numbers, and \(i\) represents the imaginary unit. For example, \(3 + 4i\) is a complex number. Here, \(3\) is the real part, and \(4i\) is the imaginary part.
Understanding powers of \(i\) is crucial as they follow a cyclic pattern:\

• \(i^1 = i\)
• \(i^2 = -1\)
• \(i^3 = -i\)
• \(i^4 = 1\)
• And then the cycle repeats as \(i^5 = i\), \(i^6 = -1\), etc.

This cyclical property is essential for simplifying expressions involving powers of the imaginary unit.

Standard Form

In mathematics, expressing a complex number in its standard form is crucial for clarity and consistency. The standard form of a complex number is \(a + bi\), where \(a\) is the real part and \(bi\) is the imaginary part. It structures complex numbers similarly to expressing real numbers, allowing for efficient mathematical operations.
For any complex number with a missing real or imaginary part, it is important to explicitly show this in the standard form. For instance, if a complex number is simply \(-i\), it can be written as \(0 - 1i\). Here:

• \(a = 0\)
• \(b = -1\)

This ensures that there is no confusion about the real and imaginary components. Standardizing complex numbers helps in performing addition, subtraction, multiplication, and division, and also aids in graphically representing them on the complex plane.

Complex Conjugate

The complex conjugate is a vital concept when working with complex numbers, especially in simplifying expressions and solving equations. The complex conjugate of a complex number \(a + bi\) is \(a - bi\). It is derived by changing the sign of the imaginary part.
For example, if the original complex number is \(3 + 4i\), its complex conjugate would be \(3 - 4i\). This operation is helpful when dealing with the division of complex numbers, as multiplying a complex number by its conjugate eliminates the imaginary part, simplifying computations.
Taking the example from the original step-by-step solution, the complex conjugate of \(0 - 1i\) is \(0 + 1i\) or simply \(i\). This transformation effectively mirrors the complex number on the real axis of the complex plane, providing a way to easily handle complex arithmetic.